It’s also almost 10 years old and not a current gen system.

Owners of Switch 2 beg to differ.

And secondly that doesn't matter when we look at the amount of sold units.

Valve can only dream to sell a quarter of those numbers.

Valve owns the market, it doesn't have to...

Also, if we're talking Switch 2, you have Vulkan support on it so odds are you would choose 2x-10x performance gains over OpenGL. It isn't that powerful. My 6 year old iPhone is on par.

People generally don't realize how much more CPU efficient calls are with Vulkan, DX12 or Metal. And especially on handhelds, the SoC is always balancing its power envelope between the CPU and GPU so the more efficient you are with the CPU, the more power you can dedicate to the GPU.