Cycling on my own is and always was the default. I greatly enjoy it, and I certainly wouldn't be posting here if I didn't. It's about letting your mind wander; exploring; talking to random wildlife and inanimate objects; playing an inverse game of Lunar Lander - jugging lungs, knees, balance, remaining contours and exhaustion - against the climb, then zooming down the other side as close to R17 as you dare; being sarcastic at the Garmin at times, but following its sage advice at others; getting utterly soaked and enjoying it; converting miles to kilometres and back in your head; stopping in random places to seek out and rectify minor mechanical niggles; the poetic synergy of woman and machine (or appalling lack thereof). Or something.
Cycling in a group is different. Pace may be faster or slower, but more importantly it's not yours or anyone else's, it's that of the group. You can talk to people, or not talk in a mutually understood way. Hearing becomes an issue. Faffing about in the cold becomes an issue. Navigation becomes an act of consensus . Disasters aside, it's not about your fitness, and it's certainly not about the bike. The numbers are less important, except where used to quantify CAKE. It's awesome fun, but it's not the same thing.
I think riding in a group makes me appreciate the place I'm riding through more. On my own, it becomes about the ride, and I tend to only stop for bodily or mechanical needs. With others there's time to stop and think. I sometimes even remember to take photos.