I’ve never heard slot 1 cards called unreliable, for several processor generations both Intel and AMD used slots for most of their product line including all the enthusiast processors.

The reason they went away is because the reason they were made in the first place went away. At the time having lots of cache on the CPU die was badly fucking up processor yields. So they moved to a slot configuration to allow the processor unit to be in pcb form with the cpu die and level 2 cache on separate chips.

A few years and die shrinks later, cache memory was much more reliable and they put it back on the die to increase performance, at which point the pcb was unneeded and the slot design was just extra cost for no benefit. Well, no mainstream benefit, for extreme overclocking builds slots are easier to cool having access to both sides of the processor.

Your assertion that the slot design caused interface problems is like saying ram sticks are unreliable for the same reasons, and slot cpus used similar click in place methods to secure them.

I ran a Celeron 300A at 504 mhz in a slot setup for longer then I’ve run any other processor, I went from it to an Athlon XP. Never any issues and I never experienced or read about any contemporary issues.