There was no cap on engine personnel costs at the time so losing engine staff to Red Bull Powertrains was probably not due to the cap. (These loss of experienced personnel likely partly responsible for the 2022 power unit's relatively lower advantage or slight deficit than previously. Of course, that is partly on Petronas for doing a poor job compared to ExxonMobil, BP or Shell on E10 fuel too which is nothing directly to do with those two operations - Mercedes HPP or Ford RBPT.)
However both Mercedes and Red Bull losing staff to other Silverstone-area teams is certainly an issue created by the budget cap.
Reasonable Formula 1 fans are more than aware that Verstappen, Russell, Hamilton, Leclerc (and maybe still Alonso and Norris) are all at a similar level. The championship outcome(s) were these Tier 1 drivers to be paired in the same car is likely to be decided by luck and circumstance (e.g., Prost and Senna with one WDC each, Hamilton and Alonso tied on points).
Formula 1 is an engineering competition. The team's chosen drivers are just the final component to get the job done. Mercedes are certainly at an advantage as the only team with two tier 1 drivers, their current driver lineup is excellent.