He was bought to play one system, he never did.
We then played him in 3-4 different systems and positions, and perhaps only one of these played to his strengths, and I don't think any of them was what he was purchased to do. He had a period of developing some sort of understanding, and looking our most threatening player, but that period coincided with Salah not being in as useful a position, and looking horrible closer to the wing. Gakpo coming in fixed our attack, fixed Salah in a more useful position, but left Nunez on the outs, with a left side that is far more defensive, and thus suited to Luis Diaz, who by the way, comes under little criticism.
And just on that point since people have brought up Diaz as though he's undroppable. Diaz and Nunez are on very similar amounts of games played. Diaz hit the ground running and was considered to be a massive success, in a team that was actually functional, but needed some fresh legs. Nunez went into a horrible dysfunctional team and is widely considered to be somewhere between a donkey, or the jury is out. Notably, the 6/10 Nunez is easily the more productive attacking player. Neither looks to replace Mane's contributions, but I can easily see Nunez scoring better than 1/2 games, whereas I don't see that out of Diaz at all, and while Diaz looks tidier on the dribble, he holds the ball too much. Robertson has never figured out how to play off him.
Nunez is not going to be a very adaptable player, but with any credible midfield, there's a chance that in certain setups he can do more of what he's good at. The thing is, he DOES have to do more of that, and I'm not convinced we have that setup, nor will I have any clue what it is till we finish addressing our midfield. Nunez has to finish more, simply, and he needs to be getting lots more chances, as the last era's forwards all did. Lastly, he looked most effective as a left sided forward, but I think we can't play trent inverted if he's going to be there, and, we can't play that setup without gakpo or with salah wide, because Salah has proven he can't play that wide role.
His inclusion next season makes more sense in two scenarios. One, where we are counterattacking, or play a team with a very high line. Two, where we dominate possession so much we can play gakpo in midfield, or we fix our midfield to the extent that we can have an AM rather than a false 9, one that actually knows what they are doing.
I'd give him a 6 for performances, and the purchase a 3 given how the season turned out. He's a project player who could really be devastating, but is that what you need in a transition? He should have cost about 30-40 million less. I think Gakpo is our best attacking purchase for a while.