I didn't say blocking solves anything or is even possible on Nostr. I was stating the problem that people try to solve with blocks.

But please tell me how I should "not allow any spammer to do that"? 

 sorry I meant to say "mute" 

 I outlined the insufficiency of mute, and also public keys are infinite so mute is kind of not a panacea too.  

 Your only option is to use intensely-restrictive relays for read. I'm sorry that your desire isn't satisfyable in any other way on Nostr, but that's just how it is