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 + ...

I find that 99%+ of sites render far better in Firefox with uBlock Origin than with Chrome. Pages render prettier, faster, and more readable. The 1% of pages that render worse are still faster and generally more readable if not quite as pretty. That's a trade I'll make any day.

I have yet to encounter a site, that wasn't broken server side in some way, that didn't render usefully.

Please cite some actual examples.

And still a better experience than chrome with ads, plus I almost never encounter a website with problems

Have you got any examples, because this has not been my experience at all.

Not even in the slightest.

I can't think of a single one where Firefox and uBO cause issues.