I mean.. Even in New Leaf, there was a point where the Nook's became kinda pointless because you would have obtained everything in the catalog. So it's not like this is something that only New Horizons has. You would get this kind of issue in any game. I'm just repeating what everyone else seems to be saying. But it's true.
I really don't think an upgrade would be that useful, other than maybe more items on display at one time. We just need more items. That's really the issue. Without new items, we would still be seeing the same stuff everyday with an upgrade.
I disagree with it being pointless. I still go in there almost everyday to buy tools because i'm too lazy to craft them. I also constantly need wrapping paper and customization kits. There are also sometimes items in there that I may want to use for something I'm doing on my island at the time.
I don't think the shop is pointless at all. I find it very useful. Where else are we going to get things like wrapping paper, balloons, tools, flowers, etc?