It's not perfect, no game is, and not even New Leaf was a masterpiece. If you think so, check it out again, and you will instantly be reminded of the many limitations and inconveniences we dealt with in the game.
Actually...
I bought New Horizons and played it for a few weeks. To make a long story short, I didn't like it! For a while, I tried to force myself to think positively about it, because I loved NL so much and I felt like I should love this game, too... but after some time, I just had to admit that I wasn't having fun. At first, I blamed my distaste and disappointment on the severe lack of furniture. However, my issues with the game are with the core design and gameplay decisions. I didn't care at all for crafting, nor did I care that outdoor design stuff had trampled all over indoor design, which was a part of NL that I loved so much. On top of that, I felt that the villager personalities were lobotomized, especially the lazies. Beau was my first lazy move-in in NH, and after just a few weeks of enduring the new lazy dialogue, it's actually kind of made me dislike Beau, now. I just felt that no amount of waiting for more furniture, NPCs, or future QOL improvements would ever make the game better for me.
So, I returned the game, and went back to playing New Leaf to try and cheer myself up. And I rediscovered what I knew to be true all along; that NL actually
is a masterpiece. I love it; it would place at least somewhere in my top 20 games. The graphics are gorgeous, the atmosphere is fantastic, and it's just plain fun to play. I can decorate both indoors and outdoors exactly how I like, and there's always stuff to do every day, even if there's not a holiday going on. What other people may call limitations or inconveniences, to me, is just part of what makes Animal Crossing so special.
My only regret is that I bought NH in the first place. At the time, I was just so excited to have a new Animal Crossing game, but if I had just waited to see that it was actually completely different than what I thought it was going to be, I wouldn't have given them my money.
As for the March update, to rope this post back on topic, I imagine it's just going to be a handful of Mario items... I wouldn't expect any other Nintendo-themed things, and I also wouldn't expect a massive update for the anniversary.
EDIT: I know I've had a history of being mean to NH (including in this very post), but I will say this, though... In spite of my distaste for the game as it is, if they introduce any really good Bowser-themed items or villagers as part of the Mario update, I will actually have to seriously reconsider trying it again to see if it's at least tolerable. I love Bowser
that much.