Not sure why you're being downvoted. It's a very valid point.

There's a common saying that you can't take your stuff with you when you die, but you can't take your memories or relationships either.

There's plenty of reasons to cultivate relationships in the present moment without justifying it by anticipating regret on your deathbed if you don't.

And there's plenty of reasons to spend this life enjoying time with yourself.

There are lessons you can learn only in deep relationships and lessons you can learn only through extended time by yourself.

I wouldn't be prepared to call a life lived in isolation and in harmony with nature a regretful life at all.