Yes I understand, the thread literally is “ How to give advices “ so I was talking about the way people criticise player in not constructive way but in a diminishing one.Some players really help the community but other are just insulting. I give suggestion to people only if I see are doing gigantic errors and they are totally far from understanding how the class work like Ice mages, SMN with no dot, Sams or Rdms with no aoe but I shut up for if I see a BRD with no heavy shot or DRG with no heavy trust stuff like that.

Yes it’s essential to read your skills and practice with it, probably many players are not familiar with this kind of games and how it works.
Unfortunately there are really little instruments of improvement and comparison for low level players to improve and understand many things. I started as BLM back in the days and honestly I never used Fire II till early 50s because seemed useless compared to Fire III that I was spamming (ok feeling silly if I think of it) then I realised how aoe work better on 3+ mobs.
That’s because the requirements in overhall are really low, no DPS checks for examples and player can complete instances easly anyway so they probably think are doing well perfectly but they don’t realise if are missing something but that is how casual contents works.
Most of new player don’t use roles at all because seems useless, especially tanks or some players don’t understand the power of dots. But nobody force them too.
Often skills itself are not fully explained and some effects hidden, like nobody tell you lucid, refresh or tactician reduce enmity or that eye x eye can be spread stuff like that.
Anyway you may be right on the general point still nodoby needs to be surprised if player underperform at the begin