Extensions, as originally implemented, are a security nightmare. That's why every browser, including Firefox, is changing the way extensions work. Firefox is keeping blocking WebRequest specifically for ad blocking, but acknowledges the security risk. Apple and Chrome are removing it, which breaks uBlock Origin.
Ironically you don't need to look any further than extensions to see the impact of giving the entire web to Chrome. Firefox said they have to implement Manifest v3 because "support for MV3, by virtue of the combined share of Chromium-based browsers, will be a de facto standard for browser extensions in the foreseeable future." Imagine what Firefox would need to do if Chrome was the only other browser, with near-total market share.