It’s a good tool and I encourage people to use it. Otherwise the asshole filter can start to take over. I’d honestly prefer someone to block me if I annoy them, rather than try to engage me in some snark-fest or pointless argument.
I also think it’s best just to block and move on if someone acts like a jerk. Don’t respond or tell them you are blocking them. Let them shout into the void.
One of the main things I look for is the person’s comment history. If they seldom post an original thought or comment and mostly reply just to be nasty and condescending towards other people, I will block them. They are basically using the people in forums as a bunch of paper targets to snipe at. Once you know to look for them, you can spot these type of commenters pretty quickly.
In highly controversial threads I will often spot new people to block that I did not even engage with.
I agree with your sentiment and I have definitely grown and my opinions have changed from the influence of people I have “met” online over the decades. However, none of the people who influenced me in positive ways were trolls, jerks, or snarky smart-asses. I really don’t think anything is lost if you block a lot of those type of people. I actually think something is gained. The amount of time and energy we are allotted to spend in this life are precious.