Look at the net spend over the last 5 years. His City is right there with many others. City has done brilliantly on the market and part of that is because the coach has a clear idea of his football and buys players that fit the style. The players he inherited that remained all hit their highest levels in their careers under him. Everyone that didnt fit his football was given the boot. Mancini and Pellegrini didnt dominate despite the open checkbook themselves and back then they actually used to outspend everyone.
His main strength is continuity and consistency. His teams play his style of football week in week out at incredible consistency and thats why they're so difficult to beat for a league title. Thats why City is now considered the default favorite for any league season before it starts. Thats no fluke he did the same at Barcelona and Bayern. Pep = very specific style of attacking football + incredible consistency. Thats his brand and thats what he does better than anyone else. Players used to go to City for the paycheck in the past, now they choose City for the football i.e to compete at the highest level and win the best league in the world. City is stable at the top.
If by miracle worker you mean a coach that can surprise as an underdog every now and then, then I agree thats not his brand at all and he'd probably never need to go to a club that would be considered an underdog and/or work on a tight budget. Thats not luck or fortune, he earned it by delivering success and stability right from the start of his career really. Say you are in City's shoes or Newcastle's you have funds and you want to establish yourself as a stable top team, you're telling me you'd rather hire Tuchel or Allegri?
Ofc any reasonable person would go for the tried and tested Pep. Only Klopp comes close in the stability of his team and they usually fall just an inch short of City