For me the turn off is the need to constantly do side quests. I would prefer to be able to do the basic story story straight away, but it seems that this is extremely complicated: you seem to need assaults and high end heavies for that.
And yes, i know that a guy did it with 4 firestarters. Guess I am as good as he is, but in any case it bores me a lot to need to do side quests after a certain point. I am at weldry's defense, and it is hard to challenge myself to keep going forward. Not moding the mechs (except adding better weapons or building official variations) is also a thing for me, so I guess I will not be able to finish it anyway.