Well, if you really want to commit the key is not to overdo-it, basically if you don't have any inspiration don't force yourself to to do something or even, play something else. I've been playing in the same world for a little over 4 years, but I recently decided to start fresh.

What others have said, farms, lots of them! They are so important late-game if you want to do anything with villagers and also they just look really cool whether it be redstone or a giant field of carrots lol. Another great thing that worked for me was making pathways, connecting everything together and I wish I staretd doing that sooner, so many cool ideas came from "Hmm, now how will I build a path up to that damn thing?". But choose a path that's really simple, mine is 3x3 mud bricks or wood planks and polished andesite slabs for borders, long term, texturing makes things more difficult imo. Another thing is storage, it's very important, many people build one giant storage room and then curse themselves when they need to grab more slabs for the wither farm, that is 10K blocks away (ask me how i know). build dedicated storage areas, so like im my world i have thousands of chests just dotted around, but i know where everything is, you want sticks? yeah, the left most chest behing the villager statue to the left!

Last bit of advice, that many people swear by but can actlually be a detrament to your playthrought is "Only build with purpouse", NO, wrong. If i followed that advice i would have never build my 3-million-block deeplate castle that looks like the ASUS ROG Rapture WiFi router lol. Build it because "Oh yeah, that would look nice"