There's a right way and a wrong way to offer advice. We can't hear each other's voices in random content, we can't see body language, so we're relying solely on text and sometimes text can be very deceptive in tone. Telling someone "I'm going to school you on x class" in the middle of an instance, without knowing that person beforehand, comes across as super informal and antagonistic, not to mention how do you even know that person knows how to play x class? I was in a Skalla run one time with a WHM who was constantly sheathing their weapon and not healing during Kelpie. Later on, during a trash pack, while things are melting under my aoe, they called me out on my rotation and said I should do a different one. The rotation they gave me didn't even make sense for BLM - there literally wouldn't have been enough mana to do it because they were telling me to avoid using any blizzard spells at all, but they acted high and mighty about it and called me a nasty word when I told them my rotation was fine (it was the one I'd learned off The Balance discord server) and were swiftly removed from the instance via vote dismiss.

The WHM I had yesterday in Tsuku Ex with me. If she thought I was doing horribly as WHM (which she must have given her comments), she could have given some pointers. She could have said "hey, I'd love to give you some advice" instead she asked if I mained healer, and when asked why she asked that replied with "just watching you." When we wiped, she singled me out with "Kiko how are u dying so much" even though everyone else was dying as well (she left the tank dead for at least 2 minutes before the wipe finally happened and any raises before that were given by the RDM or myself). If she had tried to give advice after "how are u dying so much", I probably wouldn't have listened because she was being antagonistic from the get-go with "do u main a healer" and "just watching you" comments.

By all means, open a dialogue with someone you think could improve but remember that your words can be misconstrued in an entirely text-based system and it's not someone "being a snowflake" or being too thinned-skinned, it's entirely a lack of tonal context. "You need to work on your rotation" is vastly different than "I could help you with a better rotation."