> The problem is unforced errors on the part of both Apple and Mozilla creating awful web browsers that aren't worth using.

This feels like quite an exaggeration. I’ve used Chromium-derived browsers only sparingly in the past decade, with Safari and Firefox instead getting the bulk of my usage depending on the platform.

Generally if something doesn’t work under those browsers, the top two causes are unnecessary user agent sniffing with the site working fine once I pretend to be Chrome or the dev simply not testing against anything but Chrome. It’s been vanishingly rare that the browsers themselves were the cause of an issue.