Sckharshantallas

Well I did, the Amazon Prime Video has many weird behaviors on Firefox compared to the Chromium engine, even YouTube used to have before.

Any web developer knows it isn’t as simple as “code once, work everywhere”. If companies don’t test on Firefox (which is a reality nowadays given its small market share) bugs happen in very weird and unusual ways.

If you rely on the extensions API you have no choice. If those browsers want they can just add ad blocking somehow, the code is open source. In fact Brave has its Shields applied directly in the source code without relying on the extensions API.

Nope, Shields are built into the browser itself, not as an extension which uses those APIs. [1]

[1] https://brave.com/blog/brave-shields-manifest-v3/

Because Firefox is a different engine and might not work well with certain websites.