Well, I had the opposite experience: as the developer wasn't curious, I had to maintain a codebase with custom (incredibly inefficient) SQL queries instead of a search engine, custom code for which gems exist, pages were never optimised so they became slower and slower etc. in the end a complete rewrite was needed.

As @trustfundbaby says, you can apply new techs sensibly and that's what you should do, without the extremes.

And guess what? You could actually learn something from someone else!