I used to pug them and run with fleet long ago and they were fine. If you had 4 good people you could do it. A bad one here and there, but mostly good. Today every single KAGE or infected had only 3 or 4 people and we could not request more. No one and no one understands injuries. It is funny because WOW now even pugs RAIDS and they get finished.
No, it's because the people doing STF's have gotten fed up with the crappy caliber of PUG's and have moved on to the EliteSTF channel to find teams. Every team I've joined or created in EliteSTF has always completed the mission quickly and efficiently and almost always get the optional. The difference is night and day. I am never PUG'ing STFs through the que system again.
A) EliteSTF is always busy when I use it. Maybe you're in the wrong channel. If there's no team setup for what you want, make one as most people that want to do it are waiting for someone else to set up a private match.
I am a good player. My fleet is among the best in PvP and PvE is a joke by comparison (face roll mode). We are building our star base too and we have tons of resources so that most projects are completed within minutes after unlocking. With 25 active players and half of them farming fleet marks regularly, we can afford to do STFs if we want so don't make blanket statements. Personally I'm sitting on 1400 Fleet Marks and have donated 2000 Fleet Marks thus far and I was on vacation for a week right after S6 came out.
C) People DO STF's because the gear rewards are GOOD. I like doing ground missions (STFs, Colony Invasion, Nakura Prime during FM Event) so I'm working on getting a full Mk 12 set (75 runs and counting FML) and for PvP I'd like to have the MACO Mk12 shield (again FML with the drop rate). Not to mention people can kit up a full set of Mk12 purple weapons (even if they have a Borg modifier, they're still better than what most people use).