I’m not sure you remember that era, a *lot* of people were very angry and frustrated with Apple.
Bit like every change Apple has ever made, then...
Anyway, you're missing the point, which was not re-enacting the 1998 USB vs ADB wars, but rather your false equivalence between keeping legacy ADB/Serial alongside USB in 1998 and keeping "extra" USB-A alongside USB4/TB4/5 today, instead of USB-3-only type C sockets.
USB 1 was
vastly superior to ADB/Serial, in all respects apart from availability of peripherals. Plus, aside from being pitfully slow, ADB/Serial needed completely different/separate internal hardware. Yup, you can get ADB out of a USB port with a dongle, but there is no way to get USB out of an ADB port.
A USB-A socket, however, compared to the front USB-3-type-C sockets on a Mini (which don't support DisplayPort, USB3.2x2 modes, USB4/Thunderbolt or high power delivery modes) is just a different shaped plug. The only dispute is whether
I get a $3 USB-C-to-A adapter or
you get a $3 USB-A-to-C adapter. There's no performance difference, the A-to-C adapters are actually more compact, type A sockets are better for keyboard/mouse dongles... and we still have the same number of full-featured Thunderbolt ports on your Mini as before.
If you wanted SCSI ports you couldnt get the imac at all, you were either shoved to buying a tower and a PCI card or moving off Apple.
Good job that Apple still made reasonably priced towers back then. I could really do with a couple of PCIe-to-USB-A cards but needing a $7k Mac Pro or a $1k TB-to-PCIe enclosure is a bit of a deal-breaker now.
It was completely, more so than USBA is today out of obvious necessity, ubiquitous in the Mac world, which is the portion that mattered for this conversation
The problem was that ADB ports were only "ubiquitous" on peripherals made for Apple that cost a packet. However, the PC world was using PS/2 and janky bi-directional parallel ports.
Both platforms needed USB, there was nothing else filling that role, so it wasn't really
that much of a gamble and USB devices appeared within a few years.
The trouble with USB-C was that for many, many applications it was no better than USB-A which - at 5-10 Gbps - was already "good enough" for a huge range of applications. Thunderbolt came with a huge price premium. Key devices like multi-port hubs with downstream USB-C ports never really appeared - they're
sort of here now - 9 years down the line - with USB4/TB4 hubs, but still way more expensive than old fangled USB A hubs but - if you're not paying the premium for Thunderbolt/USB4 peripherals -
are still just USB 3.1 hubs with different-shaped sockets. ...except many of them still use USB-A for anything beyond 3 supported full USB4 ports. Because that actually makes sense in a world where even many new USB-C peripherals (unless they're sold exclusively for Macs) come with a USB-A cable/adapter as standard and don't perform any better on a type C socket.