I met my wife when I was 21 and she was 19. We got married when I was 25 and she was 23.
We lived together first.
Not once did I wish I would have met her later in life. However, while she disagrees, I don't regret spending 3-4 years dating/being engaged. That was very beneficial for us in my opinion.
That may be different for others, but nothing about our relationship really changed the day we got married. We already lived together, bought vehicles together, had pets together, etc. That transition had already occurred prior to being married. We just had a really nice wedding and honeymoon, and then it was back to business as usual. That worked for me.