What content has gated you, and for how long?
I haven't even tried Thornmarch, the EX primals, and I've only fought Cadaceus twice (then the group fell apart). I just got my relic three weeks ago, so not too long. Titan HM locked me up for two weeks.

Why are you stuck here?
I cleared Titan HM on my BLM mostly legit (I survived until ~10%), but struggled with my Scholar. I'm going for all nine relics, but the blowback I've gotten while trying to learn SCH has really demotivated me. I want to clear Titan HM all the way down to 0%, but I can't bring myself to join groups because I feel like I'm holding them back just to learn the fight. This feeling has crossed over into every other type of end-game content (except CT).

Are you upset about this? (if so - why? and how can content be added for more hardcore players such as myself without upsetting you.)
Yeah, I'm frustrated. Every time I join a group all I can think about is how I'm going to be blacklisted on my server. But this isn't something Square Enix can fix (unless they provided some sort of "practice mode" for an instance). It's just the bad end-game atmosphere.

And I understand why people are frustrated, I really do. When I go into a Titan HM Duty Finder and see half the DPS under 3000hp and some of them with a <lvl50 weapon, I know we're not going to clear it. When other people die before the heart because they can't dodge, I get frustrated. But I don't take it out on them, and I try to remember that I wasn't that great at whatever the content was the first time I tried it.