I honestly couldn't play without custom content. It was mostly clothes and hair for The Sims 2 but I found I needed even more than that for The Sims 3. So far I'm not playing with nearly as much for The Sims 4 but I anticipate that will change. EA's clothing style is very opposite mine same with hairstyles. So I'll most likely be downloading more custom stuff for the game.
Custom Content is only dangerous and game breaking if you're not paying attention. I've never had a virus or anything like that from custom content. Granted I only get stuff from trusted sources that I've had good experiences with and never the gallery or back in the day the exchange. I never use the download system given by EA. I've heard way too many bad things about it.
But as long as you pay attention to what you're downloading and where you're downloading it from you should be fine.