Quite the opposite. You cannot get better quality than FLACs on a USB stick. It is literally superior to any other method of listening on the vehicle. It is, literally, the best possible audio experience (Dolby Atmos notwithstanding, though you can play that via USB too, just not as FLAC).
That sure does sound like a worse Satellite Radio experience.
I agree audio cutting in and out isn’t premium. I’m less bothered by the lack of Sirius, as I simply don’t use it, and the number of people that do is relatively small (albeit they evidently like it a lot).
I highly recommend investing in a flash drive. It’s great.
Otherwise, there are satellite radio antennas you may be able to add, but satellite connectivity simply isn’t a feature offered by the car.