I certainly agree, that sweet spot can vary from individual to individual. That's why I tried to describe it with a somewhat broad yet generally applicable range. There's always going to be a few tradeoffs, however that plays out, but that's just how most things in life tend to go.

I'd add one more thing to your stated reasons for why relationships tend to develop later on in life than they did in the past: There's far more distractions. And I'm not talking about "youngsters and their phones", but the vast number hobbies, entertainment, and general preoccupations that can end up eating up solid volume of time. Granted, in the past they also didn't have as many practical conveniences either, and thus a lot of time had to be devoted to fairly consuming yet necessary chores.

Mind you, I'm not making any kind of a moral or ethical statement when I say that, just stating it as a matter of reality. I think future generations will have a better handle on how to manage their priorities though, I've already seen this pop up occasionally with a few self-aware and observant zoomers every now and then.