Lukaku has always been a great footballer, the problem he had was that he never fit in Chelsea system so he had to be loaned out constantly when he was there, finally he figured out a way to permanently make a move. He also got injured a while back, which made him a bit slower, but he is still talented, maybe he is not as fast as he used to be, but his speed was never the intended attribute that teams looked for him, his positioning, his heading, his shooting and technical abilities were all the things that made him who he is.
On the very first game, we saw how important those are, he helped his team make a comeback on the last minutes, and that's why I think it's important for Conte to get who he wanted, and he basically got rid of Osimhen.
I think only Chelsea can't maximize his quality because in other EPL teams like Manchester United he played quite well. After that, his future became increasingly unclear because Chelsea seemed reluctant to give him a place in the squad and that didn't make Lukaku give up but his performance with other teams was much brighter.
I am very grateful if Lukaku has a steel mentality like that and wherever he plays he can always present a consistent game. Maybe I don't really care about his speed but what's more important than that is the quality of his finishing which is still maintained until now. From the beginning, Conte and Lukaku's relationship was still maintained even though they were separated for quite a long time and we know every coach only wants to see players he trusts and Lukaku gets more attention than Osimhen.