I think Shen is alright. They tried to make him more of a fighter style that leans more to tank some of the fight and then disengage, rather than going all-in with damage,like Irelia, Fiora, RIven, Jax can.
And the reason he can't do that is because he doesn't have an ultimate to use in that 1v1, because they wanted him to keep the one he has now, obviously, which is iconic for this kit.
I like Shen, and a lot of people underestimate him. They just think he is an ult bot that just snowballs bottom lane (which he can do really well). They don't realize how strong he is in the early levels, especially till 9 where he maxes his Q. His duelling power at any stage is awesome, maybe his weakest point is level 6 where he doesn't get an ulti. Level 1 is strong, with the empowered attacks, level 2 might be awkward, but level 3, 4 and 5 are strong. Gap closer with CC, a AA denial and an augmentation + the shields he's getting. When CoC was strong, he also went in, did 3 empowered AAs (like 30% of the enemy HP), and backed off, while taking no damage.
At level 9, he probably has Bami Cinder already, maybe even some more items (maybe the full Sunfire Cape, or a Tiamat), and he is very strong. The % max HP health is very strong. I still believe, based on the enemies, how fed you are and how you itemize, you might be able to 1v1 after 9. Like, if you build Titanic Hydra, while being tanky and maybe get some attack speed item, you can probably 1v1 more people that you can imagine.