This feels good faith, so I'll have a go at answering.
Benteke: Yes, most statistical analysis showed that his level had seriously dropped after injury. In terms of output, he actually improved after moving to Liverpool, but it was insufficient.
Sterling: Probably not, if you were treating Chelsea as a champions league team. If you were treating them as a mid-table team, then yeah, there is good evidence to suggest that team effects constrain attacking output in worse teams. His output had been steadily declining year on year before the move, but it was somewhat unexpected how much it declined after the move.
Thing is, this isn't really relevant, as Nunez's numbers are good per time spent on the pitch. Its not really disputable. Both his underlying are and actual goals + assists per 90 is very very good.
I promise it was in good faith
I asked because it seems that the only defence of him in this thread seems to come from stats. I'm absolutely not an expert or that well read on it but it still feels to me like there are so many flaws that they can't account for, like the style of play, how a player fits into that team, the quality of opponent he's surrounded with etc. For example, I keep reading that high value shots is much more important than finishing ability but I would argue that surely you would expect a forward to have more high value shots if they're playing centre forward for Liverpool under Jürgen Klopp than, say, Newcastle, Villa, Bournemouth or Nottingham Forest. It then can go the other way, as with Benteke and many other forwards, that it's hard to translate your game when moving to a big side because defences sit back and you can't play off the shoulder so much.
I think it's relevant for Nunez because him coming in was an attempt to change our style of play. We'd not played with an out and out goalscoring forward under Klopp, instead we had three very intricate, technically excellent forwards who interchanged at will and wreaked absolute havoc. Our one problem we did have with that front three is we often found it difficult to score in one off finals, 21/22 we failed in the league cup, fa cup and champions league to score and I think a lot of us saw Nunez coming in as a shift in style as well as a match winner, a true goalscorer and a killer who would make a difference on those occasions. At the moment he's pretty far away from being reliable in front of goal. City basically did the same with Haaland, a lot of people said their football wasn't as good as a result but his goals fired them to a treble.
The goals per 90 stat keeps coming up and again there are intricacies with that which get ignored. He has been available all season but he hasn't played well enough and hasn't fitted our style of play well enough for certain games. If he gets hooked with 20 minutes left because he's not contributed and we're looking elsewhere for goals, or the manager doesn't consider him vital enough to automatically start games, that in itself is a problem for one of the most expensive centre forwards in the world.
I hope he's a success, as always on here some people bizarrely can't take any criticism of our players as anything other than being a shit fan who secretly wants us to fail. I just find him infuriating at times and on a big night there's quite a long list of current Liverpool players I would rather a big chance fall to. I find the debate with stats interesting because it just doesn't chime with what a lot of people actually see on the pitch. The ultimate example him being described as a 28 goal a season striker because of his minutes per goal, but despite being basically injury free and available all season he again looks likely to fail to even get to 15.
I accept what you're saying in your answer there, I suppose my question was more on the topic of how much we can rely on stats as the definitive way to judge a player, seeing as they are so often used to define Nunez. I can't say I remember ever talking about Salah, Firmino and Mane in that way because they were just obviously so good and so obviously perfect fits for our team. When people say Isak for example wouldn't be an upgrade based on stats, I think that is unfair because on the eye someone like Isak seems to suit our team and style of play very well, I think we would create far more opportunities for him than he gets at Newcastle and his numbers could rise substantially. Torres and Salah were never deadly attackers before we signed them but they fit perfectly in our style of play and became the absolute best in the business.