A block function is the online equivalent of a restraining order. Imagine telling a victim of abuse that restraining orders aren’t rational. It doesn’t have to be foolproof to provide a real benefit.
That's what the hangup is with respect to twitter's implementation of blocking, and others like it. Denying specific people read access to your otherwise public content is a bad feature, and conflating this with blocking unsolicited communications from said people (an actually good feature) is worse.
Almost anything bad a restraining order seeker is trying to prevent is already illegal. Meanwhile loads of innocent people have their civil rights stripped such as right to bear arms without even a jury trial, and often after same order evicts them from their own house.
Prosecutors will sometimes force such order agreement to drop or plead charges, even when the 'victim' believes the perp is innocent and wants to be with them. There are also all the de facto orders via cps 'safety plans' that separate parents under threat of taking the children. In many case no one wants that but the often wrong cps official.