Niang will never be Adebayor or Drogba class, but I think he represents much better value than the likes of Osimhen or Edouard. Strong enough for the PL, but got good feet for a big lad, his hold up play is superior to both the other two mentioned and he can score goals.
He was a highly regarded young kid who made the jump to a bigger club too soon, they didn't know what to do with him so a ton of short term loans here there and everywhere followed, he got no rhythm or form.
Once he found a proper home again at Rennes and played regular football, started to look decent again.
Like I said, he'll never be top drawer, but I think he's a really good value option as a back up rotation, who can also play in the wide forward roles occasionally.