Yeah I'm a 20-some year FF user and when it started you had to have IE as a backup because not everything was compatible. In the late 2000s through late 2010s everything worked everywhere, then with chromes dominance places have stopped testing or supporting certain things in FF and it feels like history is repeating itself. Unfortunately you need a chromium-based backup realistically for certain sites, but 99.5% of things work totally fine in FF.