I have been leaving the FB app off my phone (Android) for 2-3 years now, and I don't miss it one bit. I was running Messenger, but that's also a resource hog.

I am now using Messenger Lite, as I am in some personal friend groups (muted) that I sometimes catch up on, and I will say that it hardly uses any resources at all. Would highly recommend it for anyone who still wants Messenger but without the bloat and battery loss.