Thanks for reading and taking the time to respond.
Yes, a large amount of design research is not valid. That's the entire point. And collaborative design work is a necessary part of the solution but that alone doesn't fix the problem. If it did our outcomes would be better. From apps, to cars, to architecture and even the way we design algorithms we continually miss the mark for large segments of the population (sometimes to very detrimental effect).
Also, the idea that "only the person itself could design for anything 'for real'" is a straw man argument, you and I both know that's not what's being said here.