That is true, but![1] This is well understood by modern conservators, so they use reversible materials as much as possible. For example paints which can be any time cleaned up with a weak solvent specifically selected such that it doesn't attack the base painting at all. The any time is a very important property here. Normal paints "set" after a while. You might clean them off the canvas a day later easily, with some difficulty a year later, and 30 years later it becomes basically impossible. But conservation paints don't do this. They can be cleaned up a day after the work is done, or 200 years after.

The other important property is that these materials are often designed to show up visibly under UV light. That way they can perfectly blend in the base paint under normal gallery lights (if desired, this is not always desired) but they will always show up for someone who investigates the painting in the future.

1: All my knowledge about the topic comes from the aforementioned Baumgartner Restoration YouTube channel: https://www.youtube.com/c/BaumgartnerRestoration

Conservators: the dentists of the art world.

Sounds like software development

This sounds a lot like software developers, except replace decade with 6 months.

“The first order of business is to blame everything on the guy before me.”