Previously, previously, previously.
I'd be vastly more impressed if they attached an A/D converter to the tape spindle and a magnetic write head to the tape and actually wrote the tape as it moved. They you could play MP3s in your classic 80s walkman.
And I'd be more impressed if it was a hot tub time machine.
But then you'd have fratboys again.
"Cassette adapters" are a real thing, meant to let people play back CDs/MP3s/etc. on automotive tape players that don't have line inputs. It seems they're not quite as interesting as they could be—in theory, one could be designed such that the rewind and fast-forward buttons worked, it could be recorded onto, and a different track could be accessed by flipping the tape.
There's also a Bluetooth one kicking around, which is a bit more future-proof but less format-bendy.
Fun fact: Apparently all the regular cassette-to-audio adapters are now too cheap to put a piece of plastic over the head and trigger 'metal' mode on fancy car stereos, which doesn't work so good. I really need to see if some scotch tape takes care of that, because it's not like I'm not ripping apart my father's Lexus's 2002-vintage "DVD navigation system" to find a spot for an aux jack.
A compact cassette player's mechanism for detecting metal/normal tape types is a the presence or absence of a hole, respectively, next to the write-protect tab. It is detected with a simple microswitch. (A recorder uses other holes, nearer to the center of the tape, to adjust bias, but players don't care about that.)
If the player is detecting metal tape type and you think your needs would be better-served if it were detecting differently, just indiscriminately cover all of the holes with scotch tape.
That said I don't think it will accomplish what you want it to accomplish, and it's not a matter of cheaper-vs-better.
Damn, thanks, I'll have to check that. I always thought it was just some kind of impedance-sense type thing in the head.
While it's possible that everything about the more-recent-model tape adapter is more craptacular than the last old one he irreparably broke, the succession of old ones were fine and the new 'hey I found this at a big box store' replacement manages to have some weird 'overdriven' audio issues that seem to coincide with the tape deck deciding it's a metal tape. And of course there's no way to override that. So at least that's how to find out.
You know, come to think of it, I've heard bad audio from some of these devices as well -- in my own mother's minivan. But it's been well over a decade since I've needed one for my own purposes, and I don't have any before-and-after experience with an adapter that actually sounded decent vs. one that does not.
There is a pre-emphasis curve that must be applied to a flat line-level signal (the curve is described in my previous link; I leave it to you as an engineering challenge to turn that into an RC network) in order to properly emulate a tape.
(All the metal/normal switching does on a player is switch the de-emphasis curve to one that is somewhat different.)
Perhaps, then, it really really is a matter of cheap-vs-better: Perhaps the new big-box-storer adapter has zero components in it, and just has a record head wired to a stereo plug....and there -really- should be a resistor or two and a cap somewhere in there, otherwise it is guaranteed to sound like crap on any sort of reasonable system.