It's not that though.
It's not that he's just had a bad patch; it's that he looks actually awful at football.
For example, as bad as McGeady is, he can still somewhat play football, so you can't accuse him of not being a footballer.
With Niasse? Honestly I've not seen much to convince me he actually is one.
So I don't think the reaction to Niasse is dumb at all - it's one of genuine, understandable confusion at how we can pay close to £14m on someone who looks like a pub player could run rings around. You can say he needs a pre-season etc. and I did agree with that at first, but he's been four months now, has had a bit of game time, and I don't think you need a pre-season to understand the basics of football. None of what we've seen thus far can be put down to just being rusty; it really does look like he doesn't know how to play football, not that he's rusty or just inconsistent at it.