New Keyboard replacement kits

[someone]

I have tried to open one up, not having much luck.

Okay, just tried again - trick seems to be to gently lever the middle part of the base plate.  Did one side, then did the other and ... the spring is now somewhere in my garage!  But I can now open them up.

Your photos show mid generation key switches.  They become lousy after repeated use because their elasticity is lost and the carbon pill doesn't make a good contact - particularly on the shift and enter keys because they're pressed hard often.
The later generation with the vertically mounted elastic pills have the opposite effect and become hard, don't flex and eventually form stress cracks thus their carbon pills don't make any contact.  The carbon compound on these pills lose their conductivity over time irrespective if they've ever been used or not.
The first generation keyswitches used metal contacts but they're a rarity.

The surface of the carbon pills is rather slick and most things slide or break off. Someone has been experimenting with cheap adhesive aluminium tape, nickel paint, carbon paint and others. The aluminium tape seems to work well. The nickel paint seems to crack off and the carbon paint's resistance seems too high.  Silver would be an option but that would tarnish over time.  Even with the successful repairs, the feel of the keyswitches is horrible.