So what exactly would fix Lee Sin then?

Let us have a civil discussion about it.

My thoughts on the matter are tradeoffs. If Lee Sin wants to Q to an enemy, I think he should be committed to the engagement. To do this, I feel as though a cd between his Resonating Strike and Safeguard should be put in place. Maybe make it scale from 5 seconds or so that if Lee goes in, he's decided to stay in, or tank some damage before going out and vice versa. This way early game, there's more risk involved and late game he has more presence.

To compensate for this lessened mobility, Lee could have strengthened offensive stats after he Q's and lowered defensive stats. Make his defensive stats stronger when he W's and his offensive stats weaker. Make it so that the Lee player has to actively decide what role he wants to function as before he goes in.

Maybe making it like this would be like a more flashy version of Udyr, but I feel it would preserve the feel of Lee Sin while introducing some more counterplay (and decisiveness) in his kit.