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Regarding the problems with Edge, mainstream websites don’t face problems — but you hit the edge cases (no pun intended) when you try to use it for smaller sites — and especially sites meant for limited audience — e.g. internal websites built by enterprises. They are often tested for Chrome and Firefox only — and maybe Safari if there are significant number of Macs in use.
I can’t really blame the developers for not wanting to waste their time on a browser with limited usage and — especially since it often presents challenges not posed by other browsers.