The same issues would continue to exists under non-fast-track, because the same things can still be passed by a simple majority. “Fast-track” doesn’t change this. Can you prove otherwise?
If there is no fast track the bill will go to the floor as a treaty requiring a Senate supermajority. Fast track is the maneuver used to change the rules. Are there other ways they could go about this? Perhaps, but historically fast track is the only one that has ever been used on treaties. The fact that our politicians prefer to call it by another name (TPA) is telling.