It's hard to throw an easy judgement on the 3-strike system because so many of us are very different with varied backgrounds and emotional states.
I started playing June last year. I reached Titania sometime in my second month. I was a DPS, had already watched a very confusing video, my experience with the various AOEs the bosses used was super low (almost inexistent), my reflexes weren't up to scratch because I always did trials only once and never did daily trial roulette, and in general I was a very confused person throughout. So during that trial I missed the stack marker and stood very confused in the middle of nasty AOE trying to figure out what was killing me and how. Someone took to themselves to berate me about "reaching that point in the game and not knowing what a stack marker is". He continued until the end of the trial (yes I stuck through it because I didn't even know I could leave) until after the end he left. I guess it was giving him some satisfaction and/or he thought he was going to make me want to learn if he told me again and again how terrible I was.
Coming from an abusive childhood and being a survivor with myriads of different mental health issues, his tirade had the effect of reducing me to tears, me begging him to stop the abuse, and then wanting to quit the game forever. I didn't quit in the end (and I'm glad for that), but also I didn't report him because I recovered my wits a week later. He should have been reported though, if for nothing else for him to learn to be more tolerant towards other people and not treat humans as if everyone is exactly the same (aka the "I am fine, therefore you should be fine too" syndrome). And I don't believe that's something that should have been struck through after X amount of time, because we as people forget easily and it's easy to say "I promise this was the last time".
My argument here is that there is no objective way of categorising infractions because each of us responds in a different way and if you start categorising like this then you are sure to leave vulnerable people out or make them feel like they don't matter.
Take another example that happened to me in January this year. I always greet the group with a "hello" but say nothing else unless there is some discussion. One person decided it was okay to respond to my hello with the F-bomb. Is that a minor infraction? A major? Something in between? Some people shrugged and said "so what". And yet I was left shaking and unable to play (and also unable to initiate a vote kick as 5 minutes had not yet passed). If you judge this minor then you belittle my experiences and mental states.
In summary, I believe the 3-strike system works well as a deterrent and I choose to believe that the GMs don't blindly enforce it but take into consideration the context of each situation and long-term history. I also believe that treating the people one is grouped with respect and kindness and adapting one's own expectations is the only way to practice the "live-and-let-live" philosophy.