Is this correct?
Also, when going on a word-for-word basis, you would never be able to retrain a class feature because it's not listed as one of the things you can retrain. Even if you could retrain your class features, what would you replace them with?
However, you are incorrect in stating that there is nothing to retrain class features to. When there was a choice, there is something to have retrained to. Virtually every class has a choice in some of their class features - Rangers: Combat Type, Warlock: Pact Type, Wizard: Arcane Implement Mastery, etc. So IF the DM allows you to retrain these class feature (and as noted in the book DM adjudications rule), there is something to retrain them to.