I don't think Rooney will be looked on as one of the very best strikers when he eventually calls it a day. He'll be considered as an incredibly versatile, hard-working attacking footballer capable of both creating and scoring goals consistently over the course of his career. A really valuable member of any squad and someone who is extremely highly rated by everyone who has managed him. We all knows that he blows hot and cold. He always has. Apparently if he doesn't score in the next two games he will equal the longest goal drought of his career. Which was, guess when? His first season at United.
So yeah, he's always been a streaky player but that's not a problem, over the course of a season or a career, providing you have other players ready and able to step up when he's not firing. It's the lack of those other players which might hurt us this season, rather than Rooney somehow suddenly being "past it".
I think that assessment may have been fair in the past, but isn't good enough for us right now. This is because our system is structured so that he is our largest and most consistent source of productivity. Rightly or wrongly, the manager doesn't seem to be willing to unleash his other players to really go out and seek goals. As part of a front two, which Rooney has spent most of his career here, things were different in the sense that, we would be an even more brilliant team when Rooney was at his best, but when he's not, we may be just a boring team where Ruud van Nistelrooy scores winners for us, or Persie or whoever. And then for a period, we had Ronaldo, who was our best goalscorer. Again, of course, Rooney was a very good player, and when on song, the headlines were 'Rooney/Ronaldo tearing teams apart'. But when he wasn't on song, Ronaldo was very capable of doing it anyway.
In today's set up, there is no room for that. He is the Ronaldo. The Van Nistelrooy. A challenge he seems to have very publicly accepted too. The likes of Memphis and co are of course supposed to help, but sadly, the responsibility is on him. You're description of him 'always being a streaky player but that's not a problem, over the course of a season or a career, providing you have other players ready and able to step up when he's not firing' doesn't work with a one striker system where he is that one striker. I'm not even singling him out, that would not work for Chelsea either, for example, given the role Costa performs for them. He may be allowed to be injured of course, because then, Chelsea will play another striker in his place and expect them to deliver. He is not, however, allowed to be a pub player for large parts of the season, simply because, Chelsea are fecked if he is. Just like Spurs have bet the house on Kane delivering this season. In such an occasion (prolonged periods of terrible form), he must be benched, as the team needs somebody in his role to deliver. Just as we do. He (Rooney) is not our Oscar, for example, who the press can say 'he's been a little off the boil of late' and all is still okay.