50F who never wanted kids.
I am lonely at times, but so are many others who have children. Most with grown children are more lonely than I am because they lose a deep connection that became central to their very being as their children grow and part. That is true even for people with good relationships with their grown children and increases with age pretty consistently in America.
There are opportunity costs regardless of how you spend your effort in this life. Parents spend most of their effort in the care and raising of another human. Even if they do a poor job of it, parenting at its bare minimum takes a lot of effort. I spent my efforts on education, work, hobbies and friends. I have money, independence and a deep love for learning. They have companionship, support systems and share a deep love with their children.
I have a lot of nieces and nephews, and they now have their own children. I love them and show up when I am needed. They do the same for me. But it is at a distance. I have never been that interested in hanging out with them and doing family things. I do attend some family events. I bring a fun energy when I do attend stuff. But I miss more than I attend and I am good with that.
Overall, I think I made the right choice and I feel pretty good about it.