I think it's an exciting direction for the series to take (ability to terraform, etc.), but the games-as-a-service model might be incompatible with Animal Crossing. It's an incredibly meta intrusion into the game that detracts from its peacefulness and escape. Waiting for the next thing, having a pace forced on us, being forced to consider Nintendo and the devs whenever we think about the game, the uncertainty involved in waiting for features to come back, and the simple fact that most players won't play as long as it takes to complete the game, but AC is always best at release. I personally believe the Wii U and Switch lifecycles are why we got an unfinished ACNH, but I worry it'll be repeated as it's an increasing norm in the industry. I dislike the MMO-style events, etc. Basically, I feel like the features and playtime in NH are allocated to activities that are less enjoyable for me as a long-time fan and less unique to AC, and waiting for them to come back causes me stress and sadness. It's frustrating to see the incredible potential of NH and realise a lot of the promised patches will simply be restoring NH to the same level as NL (if terraforming isn't all you like). The events are also unimmersive in the same way.
At the same time, the graphics are beautiful. I never felt like previous games' graphics affected how I felt about them, but now I feel like I can't go back to them. NH's quality of life changes are for the most part irreplaceable, too. I think it has one of the best changes made to the series in that villagers can't spontaneously move. While it does make it more painful to have a rotating cast, since you have to pull the plug yourself rather than allow it to happen by inaction, it makes picking up and playing the game after a hiatus a lot better. Previously, I (and other players) would not be able to resume playing the game after long periods of activity, because we'd worry so much about villagers leaving. I like the premise of the game (the getaway plan) and building up, exploring the island etc. I think there's a lot of interesting stuff in it that could have been executed better, and I feel that the devs tried to address problems that both fans and new player have had with the series historically. They just messed up in some places and didn't have enough time, seemingly.
I'd like future entries to re-emphasise living in a village with your villagers rather than the customisation, town management, etc. aspects. To me, that's the unique charm of AC - living in realtime. It's what makes it different and more enjoyable (to me) for games than farm games. NH has some problems like poor dialogue logic that also make the game get repetitive more easily, I think. But the writing is fine, no worse than NL's - I do think it's gotten blander in general over the series lifecycle, but that's not an NH thing specifically (I'm not complaining about no mean villagers, it's more of a lack of a unique voice in the writing).
I think New Leaf is the best in the series. Previously, I considered AC:GC and New Leaf to be tied as best. It's weird that playing New Horizons would change that, but it made me appreciate the perfection of New Leaf a lot more. AC is at its best when it's feature rich, when you can spend your time intentionally, when you have a choice of what to do and don't feel constrained, when you are immersed. Absence of good multiplayer is also a hassle. Basically AC should be something I can just chill mindlessly in, but I can't do that as easily, and I've never had a problem with it in previous entries, all of them had sufficient variety and I loved just talking to my villagers. The way the dialogue works now, it's more interesting when you haven't been playing. X_X
ACNH could've been the best AC and maybe in three years it will be, but I doubt in three years I will be playing it daily etc. so I won't be able to fully appreciate those changes, which makes me sad. And I don't want my interest in AC to ride on patches. But that's just kind of how it is now =/