He has Sturridge in front of him for England, which means he doesn't get the whole burden of goalscoring on himself. He was also a much bigger goal threat a few years ago, which is why he's still even considered a striker. Now he's slower and less aggressive going forward.
Even though they're not top 4, take Liverpool as an example. They have a very good midfield with a decent mix of workhorses and creative players, but they struggled for goals last season in Sturridge's absence. Do you think they would rather have another worker like Rooney or a goalscorer like Sturridge as their lone striker, all other things equal? I'd wager Sturridge would be the better fit, given that he stays injury-free, even if he's only half the player Rooney is overall. It's like Spain in the Euros in 2012. Even though they won the tournament they were extremely underwhelming in the group stage when they were playing Fabregas up front. For all their genius in midfield, they didn't have anyone who could finish all the chances they created. Would they have been better off with Rooney up there running his arse off or a poacher like Chicharito who is eager to make runs behind and getting on the end of every pass? It has nothing to do with who the better player is and everything to do with what the team in question needs.
As I said, Rooney is a great player, but I don't trust him as a lone striker in a team that lacks other goalscorers. We're asking him to be the main outlet for goals, and we don't have anyone else in the team that we can be sure will get more than 15 goals in one season. Hell, even Rooney didn't get 15 goals last season. I'm a firm believer in every good team having at least one player that will guarantee goals. Barca have three in Messi, Suarez and Neymar; Bayern have three in Lewandowski, Müller and Robben; Real Madrid have three in Ronaldo, Bale and Benzema; City have Agüero; Chelsea have Costa and PSG have Ibrahimovic and Cavani, and they've been doing a hell of a lot better than us lately. The last time we had a player like that, we won the league. Sadly, RVP collapsed like a house of cards after that one season.
I can't see us challenging for the league title, let alone the Champions League, unless we get someone who can score more goals. We should be looking at players that score twice the amount that Rooney does. The fact that such a player exists, even without considering Ronaldo and Messi, tells me that Rooney isn't good enough to be the main striker for a team with ambitions in Europe. If he has someone in front of him who can score the goals, however...