From my experience working for a management consulting firm. It’s more like everyone knows what the problems are and how to fix them, but they are too scared of screwing up to do something about it.
So they hire a consultancy company to tell them what they already knew and take the blame if something goes wrong.
“No one ever gets fired for hiring McKinsey”
There are some modders experimenting with eGPUs on the Deck, but it’s really impractical. The Deck USB-C connector isn’t powerful enough to handle an external GPU and the OS doesn’t support it.
Valve would need to release new hardware for it to be feasible.