He was Barcelona's best player last season for me, or atleast top 3.
But you can't predict how a player's career will pan out. A serious injury can change everything. Look at Fati.
Fati wasn't this good(Yamal has generational talent potential), but he had the potential to be a world class player and 1 injury looks to have ruined him.
Either way, Barcelona need to start looking after these young players as there is a golden generation emerging but keeping everybody fit has been an issue.
If everyone is fit tomorrow, Balde, Araújo, Cubarsí, Gavi, Pedri and Yamal would all start and all broke into the team as teenagers, but they need looking after and not burning out.
The Pedri situation is the most frustrating as the team play far better when he's fit, although whenever he gets back to his best, he picks up another injury and is out for a month or 2.
It's not just the young players either, but Ter Stegen, Christensen, De Jong...all suffered injuries last season.
With everyone fit, this team can beat anyone. It only lacks a top young striker really and a manager that can take them to the next level.
As for Yamal being the best ever, let him play his football.