For me personally, Franchise is just another tack-on mode I need to play for trophies, so I always end up using the Lengends team where chemistry ultimately doesn't matter. That said, I agree the amount of randomness can be a little annoying, but it does make sense from a developer's point of view; much easier/faster to create a RNG than to individually recreate extra attributes.
Good news is the more you play, the more your chemistry will grow regardless (assuming you win more than you lose, of course). I find a coach dedicated to balanced strategies offers the greatest benefits in the long run.
