Yes, trying to maintain an old version with a deceased licensing system while using newer products with new licensing is going to be a problem. Unfortunately the only way to freeze your DAW at an older version and ensure stability and compatibiltiy, is to freeze everything else at that time as well - including the OS.
The only alternative is to upgrade, and yes, it can be a pain, and expensive. This is the modern software world we are stuck with, and OS devs are at the forefront of making life difficult for everyone else. For the most part, DAW developers seem to be doing the best they can to maintain backward compatibility while offering new features.