@NameChangedSoYouDontKnowHowBrokenMyHeartIs
I don’t think many people truly grasp what singlehood is actually like.
Even more so the older you get and everyone else barricade into their bubbles.
And you’re outside, having to celebrate them, and never getting anything in return + loneliness.
But, and I mean this kindly, you seem to be fixated on the idea that there's a binary distinction between being single and being in a relationship where relationship = good, single = bad. This is really your perspective on it, it's not reality.
I certainly do know what "singlehood" is like: I was single for most of my 20s, some of my 30s and most of my 40s. I've been single more than I've been in couples.
The way you describe the states of being single and being in a couple is really interesting: you talk about being single as if you are "locked out" of something really fun and exciting. In fact often its the exact opposite. Being in an unsatisfactory relationship can be devastatingly lonely and oppressive. Usually far worse than being on your own. Even in a good relationship it's usually fairly humdrum. You talk about having to "celebrate" couples. There's nothing to celebrate, it's just normal life with slightly different logistics and closer alignment with another person.
I think what you're talking about really isn't about couples versus singles: it's about the amount of time and energy people have to devote outside of their immediate family. Someone with a FT job and kids is unlikely to have loads of free time. It's not really about them being in a couple, it's about them just being busy and tired.
But you seem to be pinning everything on this fairly arbitrary distinction about someone's relationship status. It's not the be all and end all.