Most people here are superusers, and i personally am a dev.
Off course i have tried everything possible, clean install, new profile, HW acc off, boot to safe mode etc. To insinuate that i have installed some weird plugin and even talked directly to the FF devs without trying basic troubleshooting or have some weird anti virus plugin installed is beyond weird.
I also wrote it's the same with all of my colleagues MB's (15 people).
So how is this a tantrum and a vocal insignificant minority of it comes up again and again and the post is sitting at the top with lots of people agreeing? (i know not everyone has the problem).
Your other points i don't get. Scaling should not be an issue as it's not an issue for any other apps - disabling the GPU by accident, what? All other software works fine. You shouldn't need a discrete GPU for browsing.
This issue is all over the place, here just from their own bugtracker only from the last 12 months (detailed from this post https://www.kamshin.com/2018/07/firefox-on-macos-insane-batt...):
https://bugzilla.mozilla.org/show_bug.cgi?id=1404042
https://bugzilla.mozilla.org/show_bug.cgi?id=1422090
https://bugzilla.mozilla.org/show_bug.cgi?id=1191965
https://bugzilla.mozilla.org/show_bug.cgi?id=1429522
And from their subreddit:
https://www.reddit.com/r/firefox/comments/7d6pc6/firefox_is_...
https://www.reddit.com/r/firefox/comments/7g6k9n/firefox_qua...
https://www.reddit.com/r/firefox/comments/8if1fs/anyone_else...
https://www.reddit.com/r/firefox/comments/763avh/firefox_qua...
https://www.reddit.com/r/firefox/comments/6wv0d9/why_is_fire...
And here the devs asks for help for once (and admit a problem):
https://www.reddit.com/r/firefox/comments/7g6k9n/firefox_qua...
Just searching for random posts from the last 24 hours on reddit r/mac and bingo:
https://www.reddit.com/r/mac/comments/a3gk1k/macbook_air_201...
and you can find many more:
That you suggest all of these hundreds of people are imbeciles with weird plugins is beyond disrespectful when so many of us has tried to help mozilla debugging to no effect and with little info in return. Most of us are devs or superusers - the issue has been detailed through many technical blog posts, and investigated by highly technical people thank you.