I agree the game is totally lacking in design aspects! You’re definutely not the only one looking for better build stuff. A lot of these already exist as downloads by CC creators. Try googling what you’re looking for and adding “sims 4 CC” to the end of it. There are some fantastic creators out there. You’ll have to download them and put them into a folder in your game files. I’ve never gotten a virus or anything from this. I have over 2,000 CC files in my game. It’s a very popular way to make up for the lack of good objects in the regular game.
I basically don’t use any non-CC objects, wallpapers, floors, etc. because they’re all so ugly. But until they get their act together and start designing more attractive objects, I’ll download CC instead of purchasing “stuff packs,” etc.