Comment by jcranmer
30 years ago, right before Windows 95 came out, Windows was a 16-bit OS and the modern versions of Windows no longer support 16-bit programs. PCIe came out only in 2003, and I don't know that PCIe slots can support PCI. SATA is also from 2003. Even USB originally came out in 1996, and the only pre-USB connector slot I have on my computer is a PS/2 port (which honestly surprises me). For monitor connections, VGA and DVI (1999!) have died off, and their successors (HDMI, DisplayPort) are only in the 2000's.
So pretty much none of the peripherals--including things like system memory and disk drives, do note--from a computer in 1995 can talk using any of the protocols a modern computer supports (save maybe a mouse and keyboard) and require compatibility adapters to connect, while also pretty much none of the software works without going through custom compatibility layers. And based on my experience trying to get a 31-year old Win16 application running on a modern computer, those compatibility layers have some issues.
PCIe is mostly backwards compatible with PCI, and bridge chips used to be quite common. ISA to PCI is harder, but not unheard of.
"SATA" stands for "serial ATA", and has the same basic command set as the PATA from 1984 - bridge chips were widely used. And it all uses SCSI, which is also what USB Mass Storage Devices use. Or if you're feeling fancy, there's a whole SCSI-to-NVMe translation standard as well.
HDMI is fully compatible with single-land DVI-D, you can find passive adapters for a few bucks.
There's one port you forgot to mention: ethernet! A brand-new 10Gbps NIC will happily talk with an ancient 10Mbps NIC.
It might look different, but the pc world is filled with ancient technology remnants, and you can build some absolutely cursed adapter stacks. If anything, the limiting factor is Windows driver support.