It's not an exact drop-in replacement. There are many filtering capabilities that cannot be ported [1] to MV3, filtering lists can only be distributed through extension updates [2], and filtering is unreliable.
> Injecting content scripts in a non-declarative way is unreliable in MV3 due to fact that extensions are really service workers which can be suspended at any time.
[1]: https://chromewebstore.google.com/detail/ublock-origin-lite/...