Is it just me or does it seem like 90% of the furniture from New Leaf is not in New Horizons?

That be the case in a way. Although things have been repurposed, for example the Kiddie, Green and Blue series have all been combined into the Wooden Block series. You have to change the color with the yellow box kits to reveal it. Cabin has become the stuff that's made with hardwood, Ranch stuff sort of comes through in custom designs when using other colors of it as well. Classic had it's name changed to Antique, Cabana to Rattan, Lovely to Cute, Mermaid sort of edited to Shell, Minimalist sort of blended into the light wood stuff I think, and things that also did not belong to a set or series were edited to become part of one. Example, Lazy Susan Table in NL is Imperial Dining Table now part of the Imperial series. There's some other stuff like this as well. But as of now I don't believe things like the Modern, Regal, Robo, Sleek or Balloon stuff, as well as numerous others are in the game at all in any shape yet. I haven't seen any of it online or during my adventures anyway. But I have no doubt it'll appear in an update later.

just looking at the numbers on nookplaza vs moriDB, I think it's safe to say that less than half of the furniture items from NL made it into NH

NL has 1764 furniture items. if you subtract the fish & bug models from NH (because there are a lot of them and none of them were in NL), NH only has 945 items, many of those items being new to the series. many of the old items were renamed and/or rolled into furniture customizations like tujunga said, but overall you're not imagining things

it doesn't surprise me though. one of the things I was wondering about before release was how much development time the furniture alone took since every item is clearly made from scratch. based on what we got, it probably took a lot. NL had an advantage because wii models are easy to scale down to work in a 3DS game, so many returning items in NL are assets directly taken from CF

I don't doubt they'll add more stuff in future. aside from the obvious planned holiday sets, my guess is a big chunk of new stuff will be rolled out with each new shop upgrade they give us.

still though, I hope we get some more stuff soon, because the designer in me is suffering

Also, how many DIYs were actual furniture pieces originally in City Folk and New Leaf? And Why change the names of the furniture sets?

I think nintendo have improved a lot in terms of type of furniture, the way we can interact and the new fresh image if the items! Especially when the switch is in the doc mode!

I'm really missing some of the old sets, such as Regal.  And, I am feeling very limited in terms of design, even though we've got a lot more options when it comes to customization.  But, I don't necessarily want to use the same style, just in a different color.  Sometimes, I want to change up the style altogether.

What I do appreciate is that there are a lot more items to help you complete a full kitchen or bathroom, for example.  And the HHA scoring got a re-vamp that made creating a complete house with functional rooms, rather than cramming each room with it's own specific series, much easier.  I didn't have complete sets of anything at the time I got the max score.  In fact, I reached that and blew past it with little effort.

I'm hopeful that we will see more of the old series (and new ones!) as time goes by.  I'm also still hopeful for future Nook upgrades, but I'm now not so sure we're going to get them.  I do hope I'm wrong on that front.

I can't imagine us not getting Nookingtons in this game. I really think that they are slowing us down a bit to keep TTers from getting everything ahead of everyone else,  and I don't mind that at all. I do hope they will release more furniture in the future though. Given all of that, Nooks Cranny has a good selection each day, and I like the cabinet choices.
I finally found the screen wall there that you need to be able to make the Gold screen wall!
The Ables sisters are making me and my sister broke! We can't resist buying something every day. The clothes are so darned cute!