Rules are limited (in syntax and number) and you can only ship updated rules with updated extensions (at least you can skip the queue if you only update rulesets but it's VERY annoying to do). It's also missing a bunch of features: https://github.com/uBlockOrigin/uBOL-home/wiki/Frequently-as... (I see here that replacing response body is possible with Firefox only, is that your use-case?). MV2 was miles better.