Shen is the perfect illustration of how a champion can go terribly wrong when you fail to balance them comprehensively across multiple skill brackets. By nature, Shen has an extreme dependence on team cooperation for his ult, and that alone is enough to secure him a spot in competitive play. What Riot should have done is acknowledge this, and rework the rest of his kit so that he'd have a solid baseline amount of power at low elo (which is what old Shen used to have, even if his kit was kinda boring). Instead, Riot chose to double down by not only making Shen more team reliant with his W, but also by giving him this entire other object to manage, which skewed his strength even further away from low elo. The end result is a champion who generally feels weak and incapable of doing what he's supposed to do, purely because of mechanics that only truly unlock for a hyper-coordinated team on voice chat.
Because of this, while I do think his ult could stand to get nerfed even more, it needs to be nerfed in a manner that works better at lower elo. When Shen's shield got changed to scale with the target's missing health, that did nerf Shen, but not so much for the people who were already paying attention to their teammates' health bars, i.e. more organized players. What he needs instead is something that would affect him equally at all elos. On top of this, his base kit I think needs to be redone, in such a way that it works particularly well at low elo, while remaining more outplayable at the competitive tier. In this manner, Shen should come across as a strong duelist with a difficult ult for most players, and at the pro level he should turn into a vulnerable top laner with a devastatingly powerful teleport.