> I feel like this is with 2026 view where browsers are so mutually compatible.

I wish this was the case. Unfortunately, companies that work on non-Chromium browsers need to employ dedicated web compatibility teams to either a) help website users fix non-standard (i.e. Chrome only) HTML/CSS/JS, or b) replicate Chromium-like behaviour for specific (very popular) websites so that they work "correctly".

There's also the websites that deliberately block certain browsers which is what tools like "chrome-mask"[1] are built to solve.

[1] https://addons.mozilla.org/en-GB/firefox/addon/chrome-mask/