It renders them correctly, just not always exactly the same as Chrome. It's hard to blame devs for not testing on a browser with so little market share.

Some Javascript or maybe Canvas heavy pages run much more slowly on Firefox and are almost unusable on Firefox for Android. I find that this is rare, though.

I'll keep using Firefox + uBlock + Personal Blocklist + Dark Reader + Disable Javascript + Disable CSS + Tampermonkey + Old Reddit Redirect + CORS Everywhere + Consent-O-Matic + Hide YouTube Shorts + Load Reddit Images Directly + ...