As for "bad" my midcore track record is 1st week clear on Deltascape, 6th week clear on Eden's Gate, a clear at least on Creator, all ex trials back in HW usually on the first days or weeks when they had some tuning and challenge and weren't just about mechanics. I don't log myself but I looked at logs uploaded by others and I'm usually a solid 80-percentile player and sometimes when I know an encounter and push it I've had 95%+. If that's "too bad for raiding" then okay.
I find FFXIV design favors a certain type of intelligence, namely the mathematical and logical and those who have perfect memory are good at sudoku and crosswords and whatever are usually good at FFXIV raiding.
I have quite poor memory and mix up order of sequences, when a certain mechanic is going to happen etc but in contrast I have above average performance and is considered a "strong" player in some situations. It's also why I play DPS and not healer since for DPS it's a bit forgiving even if you forget things but healers must have perfect memory at all times. DPS can be guided through an encounter by using their rotation as waymarks but healers have no rotation and must know what happens since there is no reactive healing at all (or reactive playstyle whatsoever) in FFXIV. SMN is the most set in stone rotation of all and I like it for that reason since it leads me through mechanics I otherwise forget.
In WoW this isn't a problem because it has more diversity in design. Experienced raid leaders see "okay, he's that type. Let's not assign him this mechanic but let's have him do that thing instead because his type is usually good at it" and everyone contributes.
I've found people in FFXIV who doesn't even perform half as well as me on my highest level but who learns certain patterns and memorizes sequences three times as fast.
It's this narrow approach of the game that I struggle with but it doesn't mean I'm "bad" just because my initial learning of a certain mechanic is 15% slower or so. I make up for it once I get it and usually can prog faster than those people who got that specific sequence memorized faster than me at first.
In my experience prog is slower with a group of brainiacs who get mechanics immediately, present detailed tactics for mechanics but can't perform well enough fast enough than it is with somewhat dim people like myself who don't get everything but has a few extra gears when it's needed. The best groups ofc have both those abilities but I tend to find myself with either the first category or people who have neither tactical nor individual performancewise good skills.
Category#1, the "smart but underperforming" people tend to test my patience and those who are good at both things find me mentally taxing when I don't get a mechanic on the first try.
So at the end of the day, finding a group or doing PF becomes very random and the group jumping in PF you describe can take anywhere from 1 hour to 6+ hours of failed groups even if I'm not the one holding things back. Afte r6+ hours mental fatigue sets in and anyone can start failing.
I also know high end groups where 2/8 people are actually "smart" and understand mechanics well while the rest are just doing what they are told but compensate with unrelenting energy towards raiding. As if they just don't get tired. This works too.
It is a design problem at its core and FFXIV does not in any way welcome diversity. It is a game that demands absolute conformity on all levels.
A community as quick to judge and point fingers because someone doesn't fit the exact mold of conformity required, the way you do, is also difficult to find in other games. FFXIV is black or white, fail or succeed, right or wrong and has so few greyzones and I'm all about that grey zone.