Gavin,
I agree . . . not related to sex per se (his vid was a response to a specific email question obviously) but perhaps replace references to sex with love, desire, etc.

Neutrality or fatigue?
Wanting to move away from previous patterns of emotional expression but not knowing how to interpret, filter, and/or express what comes up in a close relationship so one defaults to ‘shutting off’?
Perhaps not a signal of maturity (whatever that is) in so much as a sign you have other things you could explore

It is a meaningless “pursuit” because there is nothing ‘out there’ to pursue: someone or something that will be or act in a way toward you that you will then determine gives you permission to feel x, y, or z. . . and someone that you can then determine is worthy of your emotional attachment.

I do think age has something to do with it.
Fortunately, one’s perception does change . . . who would want to have the same type of relationship dynamics at 45 that they had in their 20’s? yikes but that can leave us wondering how to negotiate our relationships with a different play book.

But always fun to call bullshit on oneself:
Am I really maturing or am I tired of trying to get other people to meet my needs the way I want them to?
Have I become someone else but I’m judging myself with an outdated perspective (nostalgia)?
Am I really aware of how I have used all my relationships to get my needs met? (because that is what we do with them)
Have I adequately explored my definitions and assumptions (brainwashing) about romance and love and emotionally-charged relationships and openness and blandness?
Yes, who knows . . .