lots of phrases come to mind outside of the "if it an't broke" already mentioned.
KISS (keep it simple stupid)
cheap is king
Tribal Knowledge
IF JPOP did it different; we know not to do it that way
The flipper mech hasn't changed a lot in several decades; it doesn't mean it needs to be re-invented.
Quoted from gdonovan:If pinsiders ran Stern, they would be out of business in a year.
I wanna hate on this comment; a lot.
But; you know --- he has a point.