If we don't win the PL or CL then the hierarchy need to carefully evaluate the attitude of the players. You clearly need them to believe in the manager and their own ability to win. I'm really reluctant to say a manager has to win or else, because winning the league relies on so many factors, some of which are outside your control - injuries, tight decisions, other teams having the year of their lives etc.
But, eventually a narrative sticks, and a narrative of never winning becomes really hard to overcome.
I'd hate for our best players to start to think they couldn't win anything under the current Arsenal regime. Saka will be 24 in a few weeks so he could easily be here another 4 seasons and still have plenty of time to leave to go and chase trophies, but it would be so much easier for everyone if we just won it now.