You make it look as if both Kane and Kulu are slowsters - but they are not. True, neither are speedsters either but neither "clearly lack pace" either. Compared to Adama Traoré most footballers would appear to "lack pace" anyway.
Kulu arrived with a "being slow" tag that has stuck to him among some fans (I wonder if they have seen him play) but he's shown time and again that he's able to beat defenders and match most of them for pace. Yes, he doesn't have a blistering pace but he's not easily beaten for pace either - and he's generally up against the fasters players in a team: the wing-/full-backs.
Kane has also shown that can run past defenders and that his pace hasn't let him down that much. And apart from Mbappe and Haaland, no top CF is exactly a speedster either.
Besides, Spurs will mainly be up against team that defend tight, so the speed of the brain is often more important.
Thus said, no, I would not have minded if both Kane and Kulu had been as fast as Adama but that's not gonna happen.