@servantj Yeah, only doing cardio is just gonna make you look like a wet noodle. If you actively WANT to look muscular, you need to work in strength training.
I've always loved cardio too. I need to work up a hardcore sweat for a minimum of an hour a day, otherwise my depression and anxiety start to spiral. (I'm like a Border Collie. If I'm not run adequately on a daily basis I become destructive and will probably destroy your living room out of spite.)
I was running half marathons on a near daily basis and reaching 80 mpw before I got injured recently. Now I am going out of my goddamned mind. However, I have found a good outlet in dumbbell HIIT and kickboxing workouts (which I turn into dumbbell HIIT with 5 and 8 pound weights).
I was never a biggest fan of strength training either. I think a good way to get started, as a cardio junkie, is to work strength training, bodyweight fitness and dumbbells into your cardio workouts. I've found that it made me want to improve my strength and musculature and I started craving more strength training workouts.
I'm sure you also must know that strength training is important to be a better, stronger, faster runner or cyclist. Just like other sports have to train cardio and do running drills to be better at their sport, we need to incorporate strength training to be better/faster/stronger at our sport.
Also think about the overtraining injuries and biomechanical issues common in running and cycling. Start with strength training (e.g. core and back) that would help you prevent these types of injuries.
That might get the ball rolling for you in strength training and lead you to actually liking it instead of dreading it.