Not necessarily. I have joined a few groups (unusual for me as I'm not a 'herd' person) since retiring full-time 3 years ago and have not only increased my social circle but it's easier to get meet up with existing friends both near and far.
I would say that retiring part-time for a few years is a good intermediary step but if you have plenty of interests you may eventually feel that even part-time work is stopping you from doing some of the things you have always wanted to do.
I was immersed in my work when I was employed but haven't given it a second thought since I retired full-time - and I'm getting around to doing things I put on the back burner for many years due to limited annual leave.
And the joy of no meetings, no emails, no bosses, no performance targets, no frustration with one's senior management etc is beyond measure. It's unadulterated liberty!
Don't leave it too long to retire as ill-health or the Grim Reaper may strike at any time.