Let's see here.

Mechanics/gimmick driven fights where single players can hold an entire group back, regardless of gear/echo - check
Toxicity in the playerbase from preferences to hang around other players that can actually handle aforementioned mechanics - check (guilty as charged, by the way.)
Lack of meaningful "current" content that players of any playstyle can enjoy - big check
The inevitability that, due to party size limits and weekly lockouts, friends and FC mates get left out - check
A large portion of the largest segment of the playerbase (casuals) not logging in anymore due to frustration from all of the above - big check

Sounds like a pretty accurate assessment of the game to me.