This is how our GPUs should connect. Nvidia shoves 700W through those mezzanine connectors with absolutely no issues.
The modern ATX PC is a pile of hacks on top of hacks on top of hacks, on top of a chassis design from the 1980s. The AT motherboard was originally designed in 1984 for this bad boy:
That's where the original layout of "small board mounted CPU and a bunch of expansion slots on riser cards" came from. When your CPU was an 80286 that used 3.3W, just dumping the heat straight into the chassis made total sense! Not like some idiot is going to shove a 250W CPU in here, right? And we need all those slots for network cards, sound cards, modems, passively cooled single slot graphics boards, etc. Those boards are all low power consumption, no need to put ventilation around them, doesn't matter they're cramped together, passive cooling from the warm air circulating around them will suffice.
The board got shuffled around in the 90s with the ATX standard, but the same basic layout remains. It's entirely unsuitable for 500W GPUs on riser cards, and 250W CPUs on the board. We've tried to work around it with insanely large GPU coolers, water cooling loops just to move the CPU heat to the outside of the case instead of dumping it inside, crappy power cables dangling over the board to deliver enough power to these monster daughterboards looming over the rest of the system. Is anyone surprised we ended up here?
We need an entirely new architecture actually designed for the high power CPUs and GPUs of today, which will let us build smaller, simpler designs with sane power delivery and cooling.