It depends what you mean by working wonders, but the best example of it having a huge impact would probably be Leicester, who finished 14th in 2015, brought in 7 first team players (and 2 more in January) and won the league in 2016. City have brought in 6 (effectively 7 due to Zinchenko having been immediately loaned out last season) this year and won the league, while Brighton (11) and Huddersfield (12) would argue that they've had successful seasons in a relative sense.
We brought in 10 last year and like you I don't think it was the amount of players that were the issue as such, but either the quality or their roles in the team not being defined. The issue perhaps wasn't who we signed, but who we didn't sign (a striker, a left-back).
However, because of the amount we brought in, we then had a squad of close to 30 including the young players and it all adds up.
I'd rather bring in 5-6 quality players with clear, defined roles in the side/squad, than 7-8 players who haven't got defined roles/uses, even if the quality is there (I think this has been part of Klaassen/Sandro failures, and was also part of the reason Sigurdsson struggled (as well as fitness).
We have a massive squad as it is and need to trim it.
We definitely need a left-back, a quality centre-back and a back-up goalkeeper. Those are musts.
We should be targeting a powerful central-midfield player who also has quality on the ball (I think Doucoure would be ideal, and someone like Serri from Nice could also be this type of player).
A striker like Dembele I think would be perfect for us, but there isn't enough room for four strikers in this squad. This is where the manager will have to decide whether he wants DCL or Niasse to stay moving forward.
Then the other position to target could be a quality winger/wide playmaker. Lozano would be a fantastic addition. However, this would also require us to ship one of our current wingers out - I do still like Bolasie and want to see what he can do after a pre-season with us, which he has never had, but he'd be the first to go out of the current bunch. We also need to ensure that wouldn't block the path of Lookman or Vlasic.
In terms of outs, this is the big area we need to focus on as well.
Definites
- Robles (free)
- Stek (free)
- Mori (he's a liability, get rid)
- Williams (stopped being arsed last September, he'll be gone)
- Martina (if anybody offers money, he'll probably be gone)
- Besic (Boro will probably take him or he'll go to Europe)
Maybes
- Bolasie (see my comments above)
- Niasse (see above)
- Klaassen
- Rooney
- Sandro
- Schneiderlin