We've trained people for decades that if it fits it should work. Now we've got a multitude of effectively different protocols all using the same connector shape.

I learnt "fits but won't work" running 5v(worked for the 486DX2) through a 3.3v CPU(DX4 100). The nymphs decided it was too hot and left.

Since then, building your own PC has gotten easier and easier. As you say, mostly if it fits it works. Which I think is great!

But how did plugging stuff in from the outside go the other way...

I think we're talking more about end user external connections. I'm sure I don't have to tell you that back in the day a bajillion things ran through a DB-9s and DB-25s in electrically incompatible ways and how much easier it got to tech support our families with USB 1 and 2.

I absolutely agree with you that USB 1 and 2 did great things for family IT support.

But now we're at the USB 3 (and seemingly 4) stage of things - hence my "plugging stuff in from the outside go the other way..." statement.

Between varying capabilities offered through USB 3 and cables/hubs/docks that support those varying capabilities it is a bit hit and miss whether plugging stuff in will work or not.

I now know (not yet personally verified, from other comments on this article) Lightning 4 branded cables should support all connectivity possibilities and power delivery. It doesn't solve patchy device support but at least it is one step better. Connect two USB3 devices with a Lightning 4 cable is a bit silly marketing wise but at least it is easy to support.

On the very plus side, with ATX, you can't plug in the motherboard power incorrectly, unlike AT.

Depends on how strong you are.

Or smart

Building a PC should be expected to require a certain level of RTFM that I don't you can responsibly expect from people just trying to charge their phone or plug in peripherals.