Because people only care about the loot/gear they're after. The fight is just a nuisance they have to deal with to get it. You may have noticed that some people aren't really interested in playing FFXIV (or any MMO for that matter). They're only interested in getting the rewards from doing as little as possible. Ever noticed how many people will buy a game, pay a subscription to it, and then find any way they can to not play it - hacking, botting, rmt'ing, exploiting, etc?
And of course, their defense will always be "well I wouldn't have to do those things if the game didn't force me to"; 'cause you know, SE puts a gun to their head and forces them to play the game at all. And I guess not subscribing to a game they clearly don't enjoy enough to actually play ever occurs to them.
They're complaining about BLM burns no longer working because now they have to play the game more than they want to. They liked stacking BLM because it was a faster, easier path to their possible loot drop - which is, again, all they really care about.
On a separate but related note, do you know how many people I've seen who insist they don't read the mission/story dialog in a MMO because "it sucks", yet if asked, couldn't tell you a single thing about it? Their perspective is basically, "I don't know what it's about, who's involved or what the outcome is... but it sucks and isn't worth reading". Of course, were they truthful about it, they'd be saying "I don't read the mission/story dialog in a MMO because I don't get better loot for doing it".
Essentially, for them, Loot = Gameplay. Everything else = "boring, useless filler"
Part of it is my first answer - they don't actually want to play the game. They just want to collect loot, while bypassing as much of that annoying "gameplay" stuff as they can in the process.
Second part is people will always follow the path of least resistance. That is, which ever path allows them to play the game the least, and get their rewards the quickest. I'm sure you've seen the talk of "optimal" this, "most efficient" that and "fastest" or "easiest" something else?
The third part is there's an awful lot of people who don't know the game remotely as well as they pretend to. They insist on specific class setups and such because they need those setups to succeed. It's what the wiki guides say, so it's "what they must do". If they didn't, they'd fail at them, repeatedly... and then blame the game for it of course.
The remainder of your points all boil down to pretty much some variation on the statements I made above, which could all really boil down to one simple observation that pretty much encompasses all of what I said above:
Many people (clearly not all) aren't interested in the gameplay, the journey, or any of that. To them, Primals aren't "interesting lore-related battle content which they can devise interesting, perhaps unusual-seeming strategies to take down". To them, Primals are loot pinatas.