Block is an ineffective tool simply because bad actors can simply create new accounts. Mute is honestly a better option.

The person who is muted has no idea their responses are being ignored and are less likely to create additional accounts to circumvent a block.

Also Instagram seems to persist blocks for accounts made on the same device but that's been pretty hit or miss imo.

https://www.theverge.com/2023/8/18/23837494/elon-musk-twitter-x-remove-blocking