In Sims 3 we had the Fire Meter which stopped us exceeding building limits. I wouldn't want to see a return to that in that form, because it would just stop you adding anything once the meter was full and start fires. But it could always be added as a guide. It might be difficult to implement though. There are so many different platforms and hardware specs to take into consideration.
One thing that could also help players with performance issues would be to introduce a toggle to disable Townie generation. We can't do that ourselves and on console it causes massive problems. I'm on Xbox Series X, with excellent processing power and loads of memory but my game will crash if I don't clear out loads of random Townies daily. It's out of control. I don't need them either because I have enough and the ones I do have, aren't showing up but new ones are. They're also covered in all accessories, which we've reported. So when the advice tells us the Sim household total is a factor in performance, to that point I'd say it makes the need for a Townie toggle even more pressing. I've seen so many players ask for this, it's the number one problem in my game. It used to be a weekly task to delete them but now it's daily. I don't get a lot of crashing but when I do it's down to this.