I won't claim that I've read the whole thread. Here is my current view on FLs, especially having engaged into them a lot more during the current mogtome event:
I'll use the word premades liberally to describe premade groups consistently made with the attempt to win by using certain job combinations (around a DRK mostly likely) and coordination in order to stomp half an enemy team to dust. This doesn't include most of the light parties (or duos/trios) queuing up casually with friends playing their favorite non meta jobs, or just not synchronizing or using meta plays.
Personal experience
Yes, I have friends that got pissed by premades and decided to not bother much anymore. But most of them just don't care or even noticed. That's how clueless most of the pvp casuals in the intricacies of the mode are. They're queuing for their daily, and they have genuine fun with it, like most dailies. This is why I do believe the idea that it pushes away many people away from it is exaggerated. What tends to push away newcomers to the mode is the utter chaos and making sense of what's happening, and it's inherent to the mode on its own. The day they improve this new player experience to actually upgrade player retention beyond the daily roulette, perhaps the negative impact those premades are having on casuals would become more of a thing. Or perhaps i'm totally misreading the casual pvp base idk.
Fact of the matter is, that most people who like to complain and bring up moral arguments about how harmful everything is to the casual playerbase are actually self projecting, for the very reason they're good or at least decent, veteran pvp/FL players and they have enough clues on the dreadful impact premades can have. I've seen an explosion of more consistent premades grinding everything to dust notably on seal rock or shatter in the current event where you end up with 2 teams with close to 0 points and 1 with a victory.
I've been on both sides of it, the receiving end is at least somewhat funny in that I can use anti premade jobs like MNK to just kill them one by one (if the team is following, not always a given...), but this also forces me to play specific jobs in order to even enjoy the games in question. Am I gonna lose still? Oh yeah, definitely. But at least I can enjoy toying with their best players, that's the silver lining. Being on the side of the premade when you're not in the premade is the worst experience ever for a competent solo queuer for two main reasons: one, as a loose field commander, nobody needs me in that regard, and two, even if I try to participate by playing DNC, or any job helping the premade to secure their kitchen sinks, most of the time I arrive too late to matter, or my only purpose is relegated to clean up the 2 half dead enemies left. The premade already has everything it needs to operate their kitchen sink and vacuum all the opponents into dust. You as a solo queue player, is literally irrelevant, and it's the most boring thing ever.
My take on this: premades are actually harmful to the enjoyment of the mode for solo queue pvp vets, not for casuals. I'm not gonna say it doesn't grind the gears of casual dying like that, but it's just not the same for the aforementioned reasons.
Counterpoint: solo queue veterans could make their own premade groups, and I'm sure some aren't opposed to the idea (myself included), but it's like telling a CC player that they should drop all solo queue in CC and only partake into scrims or LPs. It's not practical for obvious reasons (and I also like playing solo because your premade friends aren't always there you know?).
Premades
On the matter of premades, I'm not going to fall for the low hanging fruit and blame them for all the woes in the world. They're playing with the tools they're given by SE in a pvp mode in order to secure victories. I don't know personally how they're even having fun with this because it reminds me strongly of the old 8 man full BH5 ninja premades seal clubbing during SB before the party size nerf, which was awful, where you had one group literally running around and clubbing to death casuals just hitting crystals in shatter for example, eventually leading to non premade teams just staying in their spawn and wait until it was over, and doing it again and again game after game until the premade got bored and stopped queuing (we're not rendered there yet fortunately, count your blessings). But if that's how they're having fun, then so be it.
I also do not want SE to ever remove the possibility to queue up as parties of friends, even if it would honestly probably half fix the problem by making a sizable sacrifice in social play.
Discrepency between casuals and tryhards
This leads me to the next point which is many premade players actually hoping for people to become better and learn the tools to deal with the meta, which, spoiler alert, is highly unlikely to ever happen and is at best, wishful thinking. Not only does it forces people to play specific jobs to adjust, but it also counts on the fact that casuals or even solo queue vets even want to play that meta in the first place (which is a completely different kind of game). The idea that every casual player will suddenly try and look for premade groups before queuing for their daily is frankly ludicrous. The idea that premade groups will spontaneously form up and be able to synchronize LB meta plays is ludicrous.
The problem is the mode
We can complain however we want about premades ruining games or solo queuers too lazy to find their own premades, the problem remains the mode and how it is designed and maintained. I'll die on that hill.