With Niasse, he's a quick gangly forward, hard to read and quick to shoot. Has decent awareness of team mates when it better positions and he's got a great work rate and enthusiasm. Apart from the gangly bit, the description and profile is similar to Walcott, a squad player that keeps becoming useful.
I can see why he's too erratic and why it would be an awkward dynamic to reintroduce. He was never expected to be a world beater and there are better options. When we signed him, he offered endless graft compared to Lukaku, could play up top, as sub or out wide to stretch teams. But we have DCL and Lookman who have more ability and potential.
As a forward, you'll not often get more than about 20 touches in a game and many of those are under pressure. But he'll score goals where ever he goes, just not that many of them.