The most significant changes was around the webRequest API, used to intercept and modify network requests. uBlock Origin used the API to block unwanted content before it loads. Google killed it because they want to force their ads and tracking on users.
They always were. Chrome on mobile has never supported add-ons, and that’s been the main driver of browsing for a while now.
Desktop Chrome still has ad-blockers, but they’re just less effective now, as they can’t phone home for faster updates iirc.
The most significant changes was around the webRequest API, used to intercept and modify network requests. uBlock Origin used the API to block unwanted content before it loads. Google killed it because they want to force their ads and tracking on users.