First off, I don't believe MOO is an issue if builders use it responsibly. For example, sometimes I want items to overlap archways or tuck items like plants/stuffed animals diagonally into corners. This does not limit their interactability. What limits interactability is more than one item being placed too close together. I see it a lot with decoration, bookshelves, diagonal counters, and nightstands way too close to beds. Moo is good for some things like clutter on counters, stuffed animals in corners, pictures hung perfectly, but placing things too close together is a no no. Beware certain builders (some very notable popular ones especially) who will use MOO willy nilly without caring about functionality. It might be pretty but you can't use it.
Second: clear your tray folder, screenshots, videos, and clear your cache (If I was a member I would be able to post a link of Jam Jars tumblr page to help you with this... so please like and help me attain membership)
Third, remove/update out of date mods and mitigate CC use. (I've recently been getting into CC and I like to have less than 5 script mods in use and limit myself to only 50 cc items). Clear CC from more than 3 years ago.
Fourth: Never ask teens to do their homework (Just use "careers.promote highschool" every 3-6 sim days). Never ask more than one club to meet at a time. (And I also never let my sims talk while eating and I remove all sinks). Before starting a dance battle, make sure the sim is told to set down their drink first.
Instant fix: save the game. Or go to Manage Worlds and come back. Close background programs if on a laptop or on a computer with limited RAM and processing power. Use a laptop cooling pad.
My recommended fix is redownloading iffy lots from the gallery unfurnished and furnishing them yourself. When I see a house I like I almost never place it furnished.
