I think the only way to accurately measure the effectiveness of therapy is to survey clients - something many therapists don't want to do. From my own experience, CBT Ts are often more willing to survey clients, probably due to their more goal oriented approach in general. Keeping Ts accountable in many ways would make it harder for a lot of Ts to continue using smoke and mirrors with clients. So, the relationship would still matter, but not to the extremes that it seems to with some individuals. Whether therapy would still be appealing after such changes probably depends on what clients are looking to get out of process.