I'm honestly surprised that none of the big manufacturers have put out a modern retro case. When I built my current PC in 2019 I desperately wanted a modern retro-looking case, but the closest I could find that was actually a good case was the Fractal Design Define R6 USB-C. I got it in white with a solid side panel and I like it... but that was four years ago and I'm amazed that there aren't retro-looking cases out there yet.
What I would like to see would be a modern style of case that is also modular so that you can either build a new PC that is beige\gray\brown whatever to give it a retro feel, or build an authentic retro PC with modern quiet fans and convenient design. They could make one universal modular design with a removable motherboard tray that is connected to the back and slot covers (like some used to be) so that you can either purchase an ATX version or AT version... and all they have to change is the tray.
The front bays could also be modular (at least half of it) so that you can put as many drives or fans in as you'd like. They could sell whole front bezels as add-ons so you could get the right combination of looks, cooling, drive bays and buttons. They could even sell some kind of modular panel (either as 5 1/4 bay covers or something that fit the design better) with accessories attached to them, like a very retro-looking toggle switch for power, turbo buttons, turbo displays, etc. If they wanted to be super community-focused to build a following they could even supply some 3d-printer ready models and other files, open source, for people to make their own front panel accessories... in case they want it to look just a little bit more like some old computer they had as a kid.
If I had any kind of manufacturing knowledge what so ever I'd start a crowd funded project for this (and it'd fail like 98% of them do)... but the complexity of it would likely require expertise in many areas where I have no experience whatsoever.