Late to the party, but here's my two cents on the things in this video:
Oh my god. They actually did it. The one thing I was hoping to change was more. units. And it's the exact three units I was hoping for: Medieval Melee, Industrial Melee, and the Trebuchet. This'll likely solve so many of my complaints for the game: dead-end unit trees for certain eras, more techs will be more valuable, and the best part is all of those units will mean Civs will now be able to upgrade into their unique units! This is a massive buff to England, France, Japan, Norway, Khmer, and Georgia by itself, and I legitimately could not be happier in general about it.
Spain actually looks like a functional Civ now! Armadas in the Medieval Era is actually a massive deal even on continental maps, and is potentially game breaking on naval maps. I also love what they did with Treasure Fleets; the ability is actually pretty good even when just running internal trade routes on your own continent, and they turn into baby Portugal when trading abroad. And even though I don't think colonial settling is extremely viable in Civ VI (partially because of how little land is up for grabs in the mid-game, and partially because of loyalty as a mechanic) the bonuses you get for doing so is actually pretty nice.
I like the philosophy behind the Khmer here, and it makes them less of a one-trick-pony. Even though I remain dubious about high-population strats in Civ VI, they do get a lot of amenities, housing, and food to support that about as much as the game's systems allow. I also love the rework for the Prasat; even though Martyr spam was funny, it wasn't super consistent and having a city's tourism scale with population is a good synergy. And even still, the fact that there's way more robust avenues for Khmer to go tall makes them more well-rounded in general, even if they're still a religion/culture Civ at heart. Oh, and Domreys not needing to always be hard-built makes their mid-game conquest pushes much more viable. I'm not sure if the Khmer will all of a sudden be a great Civ, but they'll certainly be a lot more fun, and that's a win in my book.
The China buff is pretty ok in my book. As I've said before, when it comes to talking about China, I think the Great Wall and Kublai Khan's abilities are strong, and Qin's ability is broken, but Dynastic Cycles and the Crouching Tiger are lackluster. This isn't how I would personally buff the ability, as I think return to how the ability was tuned at release would be fine, but this is still good. Having the ability synergize with how you typically want to play China is a really good idea, though this definitely helps Qin more than Kublai, and he was already the clearly better leader choice.
Perhaps my hottest take in regards to Civ VI is that the Mapuche were the worst Civ in the game prior to this upcoming patch. Chemamulls were legitimately great (if weirdly limiting in placement), Toqui was fairly solid, the Malon Raiders were overly niche due to needing to be hard-built (and can't upgrade into Cavalry for some reason), and Swift Hawk was actually a detriment to you, since it could flip a city you were already sieging and completely reset the health-bar. With these changes, however, they might actually be great. First off, they buffed the already good part: Chemamulls now give production too—sure, I'll take it. Toqui now also apparently gives percentage-based culture and production, which is kind of wild actually, and it really helps to jump-start conquered cities. On top of that, great news: Swift Hawk isn't a detriment now! Since you now get extra damage to Free Cities, you now have a legitimate reason to use this ability, and since the loyalty penalty is insane now for Civ in Golden Ages, you're liable to do it really quickly, so you're probably not going to experience a situation where you're trying to siege a city, some unit suicide-charges your army, and inadvertently flips the city. These improvements are legit fantastic for Mapuche, and they probably end up jumping two tiers. The Malon Raider is still awkward to use if unchanged, but if it actually upgrades from Coursers and into Cavalry, then we're cookin' with gas.
Is Canada actually OP now?? They get actually more food and production for settling in Tundra than other Civs will get on normal-settling locations. That means that you're going to have an insane amount for free land that you can settle at your own leisure, and it'll actually be really good land too! Also, Canada's Better Naturalist (by which I mean the Mountie) now is even more of a Better Naturalist: you're not only the only Civ in the game that can convert Gold into National Parks (thereby saving Faith for Rock Bands), but you now get two parks as well! Canada has gone from arguably a joke Civ at release to a Civ that I unironically think is one of the best Culture Civs in the game.
The one disappointment I think of the video is Georgia, and while the changes to Tamar's ability will almost certainly give Georgia the first pantheon of the game (assuming Indonesia isn't in it), and it's definitely better that the Casus Belli part of the ability it's supplanting, Georgia definitely needed more love than this. At least the Khevsur don't need to be hard-built anymore, which is definitely good. With Mapuche skyrocketing in stonk value, Georgia probably return to the bottom of the barrel. Unfortunate.
Some other changes I'd like to see are minor buffs to Brazil, England, France, Kongo, Sweden, and major buffs for Poland, India, and the Ottomans. I would also like to see reworks for Scotland and the Dutch's leader abilities, because while I think those Civs are actually good, their leader abilities are just useless. Perhaps controversially, I don't really wanna see nerfs for the Civs that are already really good: they're fun to play, and I don't think any of them are game-breakingly strong. I would, however, like to see a rework to Babylon: something that I think would be fair is to make them not completely break the tech tree (you can only fully unlock a tech via Eureka if you've already researched the prerequisite technologies, in return for making their early game less weak.
Overall, this patch beyond exceeded my expectations for how they were going to rebalance the game based on how they handled the NFP patches. Though I still have some gripes with some of the systems in Civ VI, the balancing changes and (especially) the new units have rekindled my excitement for the game more than anything that dropped in the year-long cycle we've been on. Also, good news for those hoping for more Civ VI content: Kevin said "the final update of the season", which the purposeful wording of which definitely leaves the door open for another pass or expansion further down the road.
Some people would agree with you, some wouldn't say they were the worst but agree that it was at the bottom of the barrel, and some would disagree with you that it was the worst. 
