Can you afford to also get an MTB? If so, do that and have best of both worlds.
Road bike to ride with friends or groups who like roadie stuff, and MTB for the adrenaline rush fun off road.
The former will keep the fitness up if you don’t MTB so often. Though if MTB is your life, just ride loads off road and you don’t really need the road fitness.
Personally I can’t see why group ride road riding would be more enjoyable. Nothing more dull than staring at someone’s lycra ass or tarmac and riding like I’d be on a cycle machine at a gym, with little variation or technique. All seems to be about rules, rhythm and speed but no actual enjoyment. Off road – fun, no rules, as fast or slow as you want, very social and generally riding in the countryside away from traffic.