Being an analytical kind of guy, when my son(doing pitching and playing two way through HS) asked me if I thought he should do Long Toss, I had to study it before I could answer him. And based on what little I could find at the time, I felt there was sufficient evidence that LT was indeed helpful. . .IF done correctly. Like any other drill, it can be done wrong and/or be abused (and from my observations, it often is when not being supervised). If one is doing LT to see how far they can throw, then that would be an abuse of the drill, which is not designed for using maximum effort and doing so is simply setting one's self up for injury. Correct LT drills can help with building core strength and flexibility, but like any repeated activity, having no other type of drills to go along doesn't provide balance to the body for effective conditioning towards that goal.
My son continues to do LT as part of his routine. He stopped being a two way player on entry into D1 college baseball and no longer pitches as he chose to concentrate on being a position player. He used to sit at 90-91 and topped out at 93-94 with his fast ball. When he hit those top velocities, I'd ask him if he was throwing at maximum effort. He'd smile at me and say, "Oh Dad, you know you don't pitch fastballs at maximum effort and be accurate." I always worried about his arm, especially since he was a two way player and often was put on the mount in the middle of a game with not much warm up. Thankfully, he's never had an arm problem to date and is starting his 2nd year of pro-ball. I don't know how much LT may have helped, but I do give some credit to it.
PS: Yes, my son did occasionally try to see just how far he could throw the ball and in college freshman year he told me he had thrown from foul pole to foul pole once. As impressive as that was to me, I really made an effort not to encourage such displays.