This is completely false. The fact that 1 exists every now and then is plenty?
It is so hard to get a learning a learning party filled. I saw my friends put up a PF for T7 the other day. The one expired waiting for a tank. They put it up again. Another 45 minutes in, still no tank.
I don't main a tank, and I've only cleared T7 using my main. But I decide to join them with my PLD so at least everyone gets to learn. After I joined I asked if there was anyone with an alt class that is a better tank? That was met with silence. I told them the more experienced tank should do OT and take on adds. That was ignored and no one said a word. But after the 5th wipe, the one time I had voice when the adds showed, and the monk got aggro on the add dies next to healer and healer ended up with the add leading to the wipe. And one them supposed "experience player" decides to take it out on me and wanting to vote kick. Obviously the vote kick failed, but then the verbal abuse started up. Yep some learning party. The experienced players in general don't want to put up with other people learning, and they don't really want to help with learning parties either which adds dramatically to the difficulty for everyone else.
In contrast what do I see most of the time. T5 farm, Levi EX no myth bonus, Ramuh EX must have multiple clears... etc. etc. Only hunt parties are more common than those, and the ever present T6-9 will sell for 60 mil party on the PF.