I hear you. Track speed aside, though, Kearse was probably the most violent player of his era. The offense would throw a bubble screen to a WR and the WR would gain 15 yards and then, unexpectedly (to me), he would be obliterated from behind by a heat-seeking missile that was Jevon Kearse. Kearse had DK Metcalf's body and he'd throw himself violently all over the field. I'd never seen something like that and haven't seen it since. He fizzled out early, probably because of how violently he played.
I don't see that same suddenness when I watch Rousseau - he seems to be more of a Gumby-armed octopus, which is fine with me - he'll probably play a lot longer than Kearse did as a result.