This may be a “safety” measure in the bios of the phone itself that was triggered when you flashed the rom. Can you try to flash back to stock android and see if that works? (Tho, depending on the manufacturer, that may be a bridge already burned.) Also, it could be that android 13 dropped driver support for the phone in question and no longer “officially” supports it, so some options are grayed out unless you enable them in developer options. Probably not much help for you, but that’s the best I can think of.
Maybe I’m just over-hopeful, but I think “generations” is far too much of an over
understatement. With the way that technology moves, I don’t think we’ll be waiting that long.