So it's sort of incoherent to talk about how "you" would experience becoming a parent, if you haven't yet, because the "you" in question becomes a pretty different person.

I'm not sure I've been deeply changed, I'd totally resonate with "become a different person."

An analogy on similar lines:

When John turned 18, he got in his car and drove from Nashville to Portland. He got a job washing dishes. That caused him to make friends with some people who sailed. In turn, that showed him how much he loved the sea.

After a round of drinks with a NOAA officer, he went applied for some scholarships, went to college and entered the service. He met the love of his life during an overwinter stint at the south-pole

At 55, John retires and starts to sail the world.

Someone asks, "Was it a good decision to drive to Portland? Would it have been better to stay in Nashville?"

A question like "does John have a good life?" is answerable. But that life is radically different than the life he'd have had in Nashville.

We have no idea what Nashville-John would have ended up doing, but we can be sure it wouldn't have been sailing. Without that image, it's almost impossible to guess if the alternative is better or worse.

Life with kids are satisfying. Life without kids was satisfying. But, even after a year, the kids have started to cause a huge shift in the kinds of things I'm doing with my life, the friends I make, and the opportunities that I'm likely to take.