These are sorted chronologically; I added more and more as I played on:
The introduction movie is very nice.
The song is actually less nice than I thought it'd be.
The loading times are surprisingly long, when launching the game, starting a game, and exiting to desktop.
Continents might be a bit silly (I discovered a new one on turn two).
It takes a second for tile information to load.
The resource icons are hard to see at a glance.
I cannot see on which tile a citizen is working without opening citizen management.
I cannot see how long it takes until a city's culture expands - but that may be my fault, for surely such information cannot be absent?
Scrolling with the mouse is extremely inconvenient; it works just below the top of the screen, but not on the top, and it causes me to scroll upwards as I hover over various buttons.
The visuals are very nice, with a lot of attention paid to them... But then there is also the terrain - such as hills - which doesn't look nice at all. It's odd.
Barbarians are very present; I met a scout on turn three.
City states are also very present - I didn't see an option to change their amount? - and perhaps they are too present, for envoys grant fancy bonuses (+2 science, for example), and you get an envoy by simply being the first to meet a city state. That's a nifty system though!
I have never heard of 'gypsum' before, nor did I know of the board game 'Senet'. Thank you, Civilization VI.
The initial four government policies are excellent. Civilization V sorely lacked strategical choices here, but VI seems to have them.
Pressing 'Enter' doesn't close windows, which is silly.
I predict tech (science and culture) choices will be ruled by 'which eureka do I already have'. Eurekas aren't a nice mechanic (both way too easy - you get them randomly - and way too impacting; I would change the former, so that they are very specialised things, almost like quests).
Don't randomly press on the F? keys; I tried finding the Civilopedia (F12 seemed sensible), and discovered that F5 quick loads (or perhaps F5 saves it and F6 loads it) the game. This is silly, for the F? keys are known to provide information, and people will press them to try them out.
I didn't understand the embassy-esque thing at first; after meeting an AI, you get a second message, and if you say 'yes', you reveal the AI's capital to yourself. That could have been clearer.
I lack a lot of information in general, from 'extra production' (what is that? +1? +100?) to 'fortify until healed' (how many turns?) and ever so on.
The diplomacy text is abhorrent; leaders mention places that don't exist, Philip's text literally contains 'etc.' (please...), and translations are inaccurate ('... is to dance with the dead' was translated as '... is to invite death'), for example.
On the other hand, Saladin's translated text rhymes nicely - I wonder if that was intentional? It'd fit him very well.
AI's randomly pop up with unskippable (?) cutscenes to tell me random things about what they like or dislike that I am doing.
You can't properly zoom out, and so, there is no overview.
A city's production speed and citizen growth and all doesn't update while in the turn; if I'm working a tile with two food and change this citizen to work on a tile with one food, the growth rate stays the same until I go to the next turn.
The day and night cycle is nice and fancy, but I eventually turned it off and put the time at 12:03 (why can't I type in a precise time?).
The music is very nicely crafted, from what I have heard so far.
The maps are way, way, way too tiny. Huge with eighteen civilisations is completely cluttered by city-states and civilisations - there's room to build two to three cities per civilisation at most. In Civilization IV, meanwhile, huge maps with 30 or so civilisations wouldn't feel cluttered at all.
The AI is irrational as ever, and the warmonger penalty is a way too limited mechanic here; the penalties are too excessive, the possibilities too limited, and all in all it leads to the whole world hating the whole world.
That also goes for agendas - there are conflicting agendas, by the way - that lead to the whole world hating the whole world.
Surprisingly, I would say one unit per tile isn't thát bad - yet - but, well, I just entered the Classical era (though, on Standard game speed with techs that take as long as Marathon in the Ancient era and progressively longer in every later era).
What are the trade delegation diplomacy pop-ups for? And why do I need all these diplomacy pop-ups that aren't instantly skippable? And why are the diplomacy screens so huge and useless, with all useful information crammed in a tiny window? There's a lack of overview and a need to scroll, despite the fact that most of the screen isn't used!
Why, actually, does the game not instantly exit to desktop when I tell it to?
And as for diplomacy; how come people are unfriendly despite me having much more positive modifiers (added together) than negative modifiers (added together)?
Why is it so hard to go back to Civilization IV regarding AI's? AI's have a peace-value (Genghis Khan would have it near zero, Gandhi at ten), AI's like other AI's with the same peace value (as well as a plethora of other diplomatic modifiers, of course), and the only kind of warmonger penalty is that for declaring war upon one's friend. That system worked perfectly.
The UI in general is a mess, as I already stated; the city screen lacks vital information and is extremely inaccessible - again, what was wrong with Civilization IV?
So, too, for things such as selecting civilisations to play with, when setting up a new game; the boxes are large (for they contain a whole icon instead of a name), you can't type in a letter to quickly go to there (pressing 'Q' should lead me to 'Qin Shi Huang'), the scrollbar is too tiny to be of much use, and the differences between the selection box and the selected box (does that make sense?) are way, way too hard to see.
Why can't I press 'M' to stop the movement command (why was this ever changed from 'G' to 'M', on that note? Nothing wrong with 'Go to', is there? Consistency is important)?
It's nice to play on Standard speed with technology being researched at Marathon speed (200% slower) in the ancient era, 300% slower in the classical era, and 400% slower in all the following eras.
The explored-but-not-visible fog of war should be in the colour of the explored-but-visible parts, and should look exactly like those parts except for being shaded. Like in Civilization IV. I mean, this fog of war was a great idea, and it looks very nice - but functionality is more important.
Why can't I rename cities? Nor units - and requiring a promotion doesn't count - nor my leader, nor my civilisation?
Why do districts not display their yields?
Why can't I destroy my own districts?
Why can't I see where my borders will grow (or when, as I already mentioned)?
The tech trees (culture and science) lack overview; the buttons are too large.
Why are Sleep and Fortify different buttons with different hotkeys? That is pure nonsense.
Why is there no overview of trade deals and the amenities I currently get from which resources and whatnot?
Why is there no build queue?
Why does the Civilopedia not contain hotlinks, and why is it so terribly uninformative in general (that goes for the whole game, mind; 'extra production' is meaningless, write '+1 production' or such - there are so many ambiguities)?
Why am I forced to use that terrible Settler lens when I have one selected (same with Missionaries and Apostles, but they're less annoying)?
Why can I not see where units are going when I select them?
Why do I not care overtly much about which technology I'm researching (because of eurekas and because there is often no real need to research something now or later, be it because the technology doesn't unlock much or because there is no challenge)?
Why do I not care about where my citizens are working (because the interface is terrible and I can't be bothered opening the citizen manager - I can't even see where citizens are working without entering the citizen manager!)?
Why do I not care about which great people I am getting, randomly getting a message to randomly grab a person and forgetting him or her a moment later?
Why are so many of my city's tiles unimproved - why do I find myself to not care too much about them (because I might put down districts there later, because Builders have a finite amount of charges and need to be rebuilt, because improvements have rather meagre yields, because I am miles ahead of anyone anyway)?
Why is the sea completely and utterly useless?
Why are units so completely messed up? Why would I choose a swordsman over a horseman (spears aren't very relevant)? Why are the upgrade paths so messed up? How can you possibly make knights upgrade to tanks, musketmen to infantry...?