Can u Be more specific with your question?
Isolation moves help with both development as well as rehab. a move like roman chair spinal erector work is not going to make your back thick or jacked. That's not the point of that move its to help stabilize and strengthen the lower back which in turn will enhance all your back lifts.
I feel isolation moves are crucial. They allow a person to learn how to contract and really target that muscle. Once u learn how to really contract and use a muscle then u can also get more out of your heavier mass moves by being able to feel and use that muscle working even with heavier moves.
I've seen some guys dead lift some heavy crap I could never lift. There backs were nothing crazy by any means. I do still feel deads are a great back mass move.