As a younger person who missed out, I recently enjoyed this mini-documentary— especially the surprisingly lengthy history of the many devices for a supposedly "failed" format: https://www.youtube.com/watch?v=kU3BceoMuaA
Console MD player/recorders were ridiculously expensive in the US. Portable players were expensive but not nearly as bad as the mains powered console ones. This meant most people just went for CD players.
Because they didn't sell well here music labels didn't release many (any?) MD albums in the US. That meant you were buying new albums from the "import" section of the store (if you had a record store that sold imports) for full integer multiples of CD album prices.
Unless you were stupid rich then you bought blank MDs and recorded your own music on them. That didn't mean dropping tracks onto a playlist and pressing the "Burn" button. You had to plug your MD deck into an audio source, hit record, and then play the track/disc back in real-time. If you just did a whole CD at once it would record as one long track but you could go back and mark start and end points to break it into actual song tracks.
So you either spent tons of money buying commercial MD albums or bought blank discs to make your own. Making your own discs meant every album you listened to required the cost of the blank disc and at least an hour of your time to record it.
Or you could just save yourself tons of money and effort and listen to CDs.
Source: a friend of mine was obsessed with MiniDiscs and I thought they were cool until I spent an afternoon recording two discs. I realized my DiscMan was a way better deal.
If you were loading music from MP3 or WMA the software was transcoding those formats to ATRAC, NetMD players didn't natively support either format. So you went from one lossy compression to another. If your MP3s were already at the minimum threshold of quality because they came out of a shitty encoder they were just going to get worse in ATRAC.
If you were loading WAVs into SonicStage your quality would be way better but you first had to rip your CD to disk and then load it in to SonicStage. So you had no time savings over ripping to MP3. ATRAC also had a bunch of DRM so it limited how many discs your could load a track on. Not an automatic problem but putting a song on more than a couple discs wouldn't work.
Keep in mind that by the time NetMD players were out CD-R drive's were cheap and pretty common. A lot of CD players had also started supporting native MP3 playback and dedicated MP3 players were readily available.
The extremely inconvenient NetMD experience was up against cheap CD-Rs, much more convenient MP3 players (including the iPod), and in general a better MP3 experience. The whole MiniDisc ecosystem was just inconvenient unless you had spent a lot of money to live in some sort of end-to-end MiniDisc world.
My apartment was burgled in 2003, and the insurance payout covered an iPod to replace the stolen minidisk player.
Night and day, no comparison, that iPod was the coolest thing I owned at the time, and stayed that way for many years. It's in storage right now, but the last time I plugged it in, a couple years ago, it still worked. The battery is toast, though.