This feature is requested every few months going back to the beginning of the game. There are tools to create a Zwift workout from a GPX file, but riding an imported route is not supported and doesn’t seem to be on the roadmap.
Latest RGT offers bots on magic roads. Still boring in my opinion, but a bit better. It’s also possible to have group events on magic roads if you can recruit other people to ride with you. A local club here held a virtual race earlier this year using data from a local route.