The context from the GP is relevant, my reply was to say no don't accuse laziness and ignorance, I do use FireFox as my daily browser, I did test with FireFox, I wanted my page to be equally good and I couldn't achieve that. The effort of rewriting to get 'great' responsiveness in Edge got 'sub-par' in FireFox - and it's not because I didn't bother trying.

Your last paragraph is probably true in general, and true specifically for me because the Windows server I was using had Edge and didn't have Chrome or FireFox.