Ok: still, no car stereo runs such poor compute that it can't handle loading and sorting 15k songs if it supports them at all. Any size you moved to is still at most an order of magnitude more and 10s-20s is not six minutes that was mentioned.
It’s more likely poor programming than lack of cpu power. I personally prefer filename sorting rather than metedata sorting for this reason.
There’s very expensive stereos that might do it but they tend to come with Android etc, and those companies don’t want you to be self-sufficient.