Well on Lemmy it’s fake control considering this system wasn’t really designed to safeguard against malicious actors but rather to stop snowflakes from being offended.
Also the instance blocking feature doesn’t even block users, which you and everyone else suggesting people use it would know if you even read the changelog for 0.19 and saw this little qualifier right here:
Users can now block instances. Similar to community blocks, it means that any posts from communities which are hosted on that instance are hidden. However the block doesn’t affect users from the blocked instance, their posts and comments can still be seen normally in other communities.
If you want real control yourself what you need is your own Lemmy instance, or to co-operate a Lemmy instance with somebody else.