Leon’s best comparison for skill set has always been Big Joe. He slows down the game in a good way and I agree like Joe he will age well.
I think his best comparison coming out of the draft was Jumbo. I think he evolved more into a Malkin type player. Much more of a goal scorer than Joe Thornton.
That being said, Malkin is also a player who has aged incredibly well.
Draisaitl is also a very smart player with a true commitment to getting better and adjusting his style where necessary. Who would have thought when he came out of junior he'd have become as strong a skater as he became or as good of a goal scorer? He recognized that if he was going to be able to play with McDavid those were the two things he needed to work on and became elite in both of those areas. As he ages and starts to get a bit slower and such, I imagine he'll continue to adjust and work on his game so that he can continue to maximize his contributions on the ice.
That being said, even guys who age extremely well like Malkin and Thornton, those two were largely done being in the conversation as a ~top 5 player by the time they were in their early 30s. I don't doubt Draisaitl will remain effective late into his career. But it's unlikely that he'll be able to provide the kind of value later in his career that his contract dictates he should be providing. Although with the way the cap can increase that might be less of a concern.
Either way, thats not a reason not to sign the player. Just need to accept that he's probably not going to be a top ~5-10 player for the back half or 2/3rds of the deal.