In-Game Parser.

[Felessan]

i think what he mean is Tank and healer get call out for doing bad job and why DPS jobs is carefree.

Even for healers/tanks the only metric we have now is whether someone died or not and whether tank can hold agro or not. Like DPS can do at least some damage and dodge mechanics or not. But we don't get specifics.
Parsers on other hand will not affect only dps - good one allows to track HPS and overheal% as well as damage taken and tank cooldowns, so there will be additional info for insults even for non-dps classes.

I dont understand why we dont have a built in parser already. How are we supposed to improve if we dont know we suck?

You don't need a parser to have a good performance. Anyone can go to forum, read about proper rotation and train themselves on a dummy to automation of perfect execution. For most people who are underperforming the main problem lies in not that they don't see numbers, but that they are ignorant to the proper handling of their class and no parser will fix this.
The only thing where parser is required when you want to achieve extreme results, but this can be done via teamwork with some PC friends and a whole another level of dedication.

if I'm allowed to kick healers who can't keep people alive through reasonable damage, why should I not be allowed to kick a dps who can't attack his way out of a wet paper bag with a hand grenade?

I am against kicking anyone, be it dps, healer or tank in DF parties. DF is for helping people, many got their bonuses from that. PF is a different story and no one is safe there, dps can be kicked as fast as healer/tank if leader think they are underperforming.