FF14 is not made for hardcore players.

[Veis_Alveare]

Simple solution to this. Vet the person you're going to help to make sure they want or can even handle constructive criticism(some people just aren't equipped to)

If someone can't handle constructive criticism they shouldn't be playing a game with other people where they may underperform.

[MagicAura]

If someone can't handle constructive criticism they shouldn't be playing a game with other people where they may underperform.

Your assumptions and elitism are stunning. You have absolutely no right to dictate who "should" and "shouldn't" be playing this game. You have no right to judge anyone, no matter how they perceive your "constructive" criticism, especially given that you communicate through an imperfect medium of hastily written language in a chat, where your good will may be completely missed on a person who may be triggered to rage by a random word.

You don't know who is on the receiving end of your "advice", what language they speak, whether they function under similar assumptions as you, you don't know anything so you have no right to judge them. The best you can do is get off your high horse and ask politely if they want advice at the end of the dungeon run. If the answer is no, then move on with your life. You can't force improvement on people if they don't want it.

[TribalReturns]

If someone can't handle constructive criticism they shouldn't be playing a game with other people where they may underperform.

You definitely sound like part of the problem here. You really shouldn't want to dictate what people should or shouldn't be doing. Performance is little to no issue in normals dungeons/trials and even experts(at a certaint point)in every expansion. ¯\_(ツ)_/¯