I agree with you. Both of my diagnosesis were somewhat subjective. The shoe store guy and the trainer at OCS who was a contracted Physical Therapist. Who knows how qualified either were. The pain was real though and the pain went away after I changed my shoe and started squating, deadlifting, and cleaning. Of course this took time.
I wonder who IS qualified to do anything other than sell me a shoe or an insert? Does anyone ever go to a podiatrist complaining of foot pain and not get fitted for a set of orthotics? The logic behind orthotic inserts is to fill the space between your arch and the ground with rubber and this is supposed to mold your foot into the right shape and that will make it strong. This is not analogous to a weightlifting belt which makes your abs and back work harder and as a result they get stronger. It just completely supports your foot by creating a false arch. How can any part of your body get stronger if it is never required to support a load?
I bought orthotics from a chiro who said I needed them (way back in '99 or so) for running. I ended up getting plantir fasciitis from them (these were fairly hard leather). I complained to the guy who said I needed to toughen up, they were good for me. I listened to him for a while but I eventually defeated the ortho's with shims made from cut up pieces of other inserts. Now I don't use them at all.
Since I got my lifting shoes (and started lifting) my feet have gotten a lot stronger and I don't miss the ortho's at all when I run.
I think the quality of orthotics has improved a lot since then, though.
YMMV.