I use Firebase hosting for a static site that gets between 100-400gb of traffic per month, and it works out a bit cheaper than Netlify ($15-$50/m vs. flat $45/m). I hardly ever use their web interface and just deal with their one line CLI.

My biggest concern with Firebase is if it's still going to be around in a year or two. That's why I'd be reluctant to use it for DB and auth stuff. I narrowly avoided jumping into Parse back in the day before that was shuttered so I'm wary.