“if it ain’t broke, don’t fix it”

“better the devil you know than the devil you don’t”

“old is gold”

“stood the test of time”

The opposite of Chesterton's fence is "Chesterton's facehugger". Sometimes, when you discover something bad, the best strategy is to immediately try to remove it as quickly as possible, before spending any energy trying to find out why it appeared.

Not sure it fits, but I like The Gods of Copy Book Headings

https://en.m.wikipedia.org/wiki/The_Gods_of_the_Copybook_Hea...