He missed some real sitters last year, but new league etc. etc. Strikers especially need confidence. His record will have loads of sub appearances, so the games vs. goals stat will be a tad unfair to him.
Luuk de Jong has recovered from his stint in Germany and with us for PSV, so it might click again for Riviere, though maybe not at Prem level. What is for certain is that with 3 points from 7 games and few chances created, we cannot afford a striker who missing clear openings like Riviere did last year. We need players that can produce right now.