I agree with 1), it´s by far the biggest flaw in Civ VI. Civ V you would have Warmonger Civs steamrolling, Civs getting eliminated by actual combat, and Ai that could actually win. Civ VI the AI can't do that.
As for 2), though I think Civ VI still have a bad pacing, you progress way too fast through the tech/civic tree and completely out of pace with age, I honestly don't have an issue with production, aside from some stuff that are more expensive than they are worth. It doesn't take 20 turns for me to build stuff (standard speed), aside from first district in new cities and anything in a city with really bad production that I probably had a good reason to settle. In a decent but not great city, it usually takes around 10 turns, while in my capital and other production cities I mighty have been blessed with it can go as low as 1 turn if I really nail my production but 3-4 turns is more common. On top of that there's chopping and Magnus, which speedy up things considerably. 20 turns definitely isn't my experience aside from cities with bad production and early game, when I still settling. By the time I win (usually around turn 260 though I been setting new records lately), I built most stuff I unlocked, not all in every city but everything was built somewhere, I don't feel like I have to ignore stuff because I can't build it.
For me the problem is more on how easy it's to progress fast through the tree, definitely way faster than the AI once you get things going. By late game, you can make 800-1000 science while the AI still at 100-150 and they get a nice bonus. R&F made some changes to slow down progress but in practice it didn't make much of a difference.
3) for me is a problem with the difficulty, I prefer Emperor and recommend it. Immortal/Deity doesn't get harder, it gets more annoying, force you into specific strategies and reduce your options. The bonuses give the AI a better early game but that's about it, once you catch up and you will catch up, the AI can't compete. At least on Emperor I never felt forced into specific strategies, main reason why I recommend it, you gonna have a weak opponent that can't win for most of the match either way, so why suffer an annoying early game that force you into strategies you don't want to take? There's no such thing as hard in Civ VI unless Firaxis improve significantly the AI. I lost games in Civ V while trying, lets say, unusual strategies, the AI can punish you if fail to keep up, which I managed to do. That's is impossible in Civ VI, there's no way to lose to the AI, in any difficulty, unless you do something spectacularly wrong like playing tall

.
4) coastal cities are way better than before, mostly because of Liang and Auckland if you get it but they still could use more love and attention, so I agree.
5) I disagree that it's impossible to have colonies. One city colonies? Sure, that can be hard but if you plan and settle 2 or 3 cities, it isn't hard to do it. I like how it demand some planning to do it, to be honest.
6) Tourism definitely would be better if it had more use other than Cultural Victory, though I will disagree that it's all or nothing because to focus on tourism, you focus on culture, so if you decide to change strategy for some reason, you have a Civ with strong culture, that will get you tier 3 governments and some powerful policies earlier. You also have to invest in science for cultural because you want to research computers and double your output, so even though you won't invest as much as you would for scientific victory, you still should have a pretty decent science. I don't see how having a Civ with strong culture and science is all or nothing. I get your point about tourism and agree but going for cultural won't make your Civ inflexible as you describe.
7) yeap