Agreed, on that - but let's be honest with finances effected by COVID it's not going to happen that quickly.
Unless Martial can find his form of last year and consitently perform i'd say that's the most urgent position of all. Right wing can be covered at an OK level by James or Greenwood. If money grew on trees then yes all 4 would definitely make us challenge next year as long as the team were motivated fully.
Oh I agree no chance of it being sorted in a year. Though I'd argue opposite, that right wing we have nobody really natural there and it's by far our weakest position. Striker this season has been a problem but Martial is better than this and you'd expect him to bounce back next season, and Greenwood has big potential and it'll be as a striker, because he will never be more than average as a winger. It's easier to sign a winger than a striker so I wouldn't argue get Haaland, but equally I think our best chance internally of the right wing being even an acceptable level would he in 3 years when Diallo can have a bigger impact, nothing from any of the senior players, so it's definitely an ongoing issue.
There is a world where we sign Sancho to sort out right wing, Martial bounces back to last season level, Greenwood makes a normal step up that we know he has the potential to do and he is expected to do after a down second season (again, normal) and we are pretty ok at striker. I don't think there is a world where Greenwood turns into a top class right winger or James is anything more than an average hard working but low creativity winger, in which case creatively we still rely completely on Bruno for creativity. So right wing will be a problem until we buy, or just wait multiple years and hope Diallo can step up, but that won't be anytime soon as he is so young and tiny.
Midfield and defence also isn't sorting itself out internally. The only one of the 4 that has a chance to sort itself out internally within the next year or 2 is striker, as Martial is better than this season, but also and more importantly Greenwood has huge potential as a striker and it's a matter of when, not if he becomes our striker.