Ok 2 things:
1)What you said about the Mane 6 being useless lately is a ton of bullshit (is a criticism I can accept only for S6, and about a pair of S8 eps);
2)A series finale is a series finale, and focus on the main characters is still due, no matter how much you feel about them, so accept this or get lost;
3)Coming to hate retroactively their past episodes only because a few bad apples in the present is fucking retarded.
If you really claim to be an MLP fan, then you should really revise your priorities, or just find another show to watch. Liars and traitors are not welcomed....