Film scoring is indeed A JOB for many. Not their passion.
That’s a bit too hard. If you have to or want to make a living of your passion not every project you work on is and can also a passion project at the same time. Same may apply to playing in a pub where hardly anyone notices you or playing on weddings or whaterver. You really have to be in a position to afford to do only passion projects. Someone like John Williams can do that after he got his break with Spielberg. Also artist in general often have an rather ambilvalent relationship to their own work and especially older works they may consider not perfect from the currentt point of view.