Made CL final with PSG while matching his predecessor by winning domestically quadruple. Winning domestica quadruple with PSG alone is not superb feat, but making CL final with PSG where players' ego is unchecked, on top of that is a mark of making step into the elite area.
Tuchel may not be a storming force as Pep, or Klopp, but he has made solid step proving himself in different aspect: surviving rebuilding under shadow of Klopp, winning domestic cup with Dortmund, learning to manage ego at PSG, and actually progress with his coaching, meeting standard set by his predecessors, then surpassing them. He's not still unproven like someone as Poch in term of ego managing, or lack of progress in CL like Conte, or how Zidane is gonna do with a team that lack financial power and elite aura to attract top players, Ten Hag's unproven at managing in top league...