The problem is this would have to wait until the end of the season and the way things are going, City will not qualify for Europe which might make it difficult to make the quality signings that are needed. It seems to me that someone more short term is needed to turn the tide.
Another issue is that the players who are not at the end of their time here (Haaland, Doku, Gvardiol etc) are not being maximized under Pep's style. So to me it looks like a good moment to start a new cycle, where a new manager is given half a season as low pressure adaptation period, short term reenergizing the team with fresh atmosphere, get the most out of the current group, reach the CL, then get players in the summer that would complement the current ones in his vision. And I honestly believe that these players need a more quick transition kind of coach.
I understand City fans are very attached to Pep because of the success he's brought but its always better to leave before you become a villain. And knowing how Pep is notorious for his burnouts and needing time away to get his mojo back and then find a new challenge, I simply think its better to be proactive than reactive.