Polyamory + Aging = Loneliness?

Not sure how much advice I could give, but as a general observation I found much of that list to be very similar to my brothers problems and he isn't that old and is not Poly. The longer you wait to make a long term commitment to one person, whether it be a poly commitment or standard one, the more lonely you get for many if the same reasons you mentioned. Good luck to you
However, until I got to the end of your post I assumed you were in your 50s/60s...are you telling me you're only in your 30s???? All this talk about aging and ending up alone...really???

I agree. I think it's too soon to feel left out of the love pool. Most poly people I know are older than me, and I'm 43.

I really enjoyed your post; a very thoughtful look at the potential downsides of polyamory. So much of what I've read about it is written by poly practitioners/advocates. It's like trying to find out how good a make of car is by talking to the car salesman. As an old person, I think much of what you say is true of anyone with age, regardless of their relationship orientation. Our choices get limited in many ways, and people tend to hunker down into some configuration as they age and stay there until the end. We're less open to change, unfortunately, and opportunities dry up. I think age needs to be re-defined like relationships, and looked at outside the usual box our culture puts it in. You're alive until you die. Live that way
Shipwrecked, I have to say you've brought some wisdom to the table with your post. You don't seem depressed to me...simply realistic. What I really liked was your analytical approach about the decline of certain groups over time and tendencies towards monogamy.

As a 42 year-old with a 20 year-old primary, I can tell you, what you're saying rings true. Of course, dating in your age range does help, but that's only one factor. Attractiveness is more than outward appearance, but outward appearance is indeed a major factor at the attraction stage.

I didn't see this as an assassination of polyamory, simply realism.
Second on OK Cupid. I found a date within 2 weeks, and while we're no longer seeing each other, we remain friends. And it never hurts to have more friends.
In my area, OKCupid and Plenty of Fish aren't too great, but that's only because of the selection pool. Your area might be great. Tinder is more of a hookup app, but it's very age-centric in the extreme.