My cadence tends to stay way down. For me, the issue is my knees. I mash, they scream. I try to spin, they scream. Needless to say, I'm quite a pokey rider thanks to that. On flats with little wind, I can hit around 14 to 15 mph. Hills with my knees, anywhere between 5 and 1

. My average tends to be around 10 mph. I may not blaze through the countryside, but I do cover the miles.
And yes, I've been properly fitted. My knees can cause severe pain when I walk up stairs, steep hills, or sometimes even when I try to sit down in a chair. So, it's not my bike. If anything, cycling if I'm careful is one of the few painfree and therefore FUN active things I can do.