Previously, they were handed the worldwide successful brand of Love Island. To me, that should be hard to screw up, but I'm guessing (like you said) that the audience for CBS is just much older. So it only lasted three seasons. My guess is The Real Love Boat was their attempt to develop their own brand along the same lines.

Peacock has the Love Island USA license now so hopefully it continues successfully over there (although I wish it were airing over the airwaves as well).