what I don't understand is why anyone thinks their opinion of the interview (or anything) matters
Thanks for saying so. Much as I would like to, I don't understand that either. Might I suggest the What is "Mind" thread, or some light reading on evolutionary psychology? Please share with us if you do reach an understanding.
I expect Alex will keep spending his time climbing.
I don't think my opinion matters much. It's just a conversation - a chance to chat with others and see what they are thinking, and occasionally to pat someone on the back. It matters to them.
But it is mostly just entertainment, and no one is obliged to read it.
Nice interview. Kimmel seemed to have had fully understood free-soloing before the interview. I wonder if they chatted before or if Kimmel already knew the nooks and crannies of climbing. Alex did a great job. Good posture too.