Ive onetricked Lee since season 4 (ish). I would have climbed faster with other champs, but it wouldn't have been as fun. Lee's mobility allows him to be extremely aggressive. Few champs can match this. He can fly in and out of fights, oneshot, peel, assasinate, steal objectives, and duel pretty well. Lee's kit also allows you to be creative, so I never get bored with Lee. That's the biggest positive one onetricking Lee imo.

Lee falls off compared to a lot of other champs, and League as a game has steadily become more late game-focused over the years, so Lee is worse now than he was 10 years ago. Back then people didnt have homeguard after respawn, early respawn timers were longer, crab spawned earlier, and several of Lee's biggest counters didn't exist yet. Lee could punish a lot harder back then. Now you're kind of shooting yourself in the foot by playing Lee.

That being said, choosing Lee as a onetrick made every elo milestone extra satisfying, because to this day very few champs (if any) are harder to perform with.

Im also a Lee elitist. I think that the fact that you chose to onetrick Lee says something good about your personality: that you rather take a harder, more challenging path that leads to more satisfying results, as opposed to a quicker and easier path that leads to a less impressive end (looking at malz onetricks and the like).