Why do we bike?
The answer in my case: Exercise.
I do over 10,000 miles per year biking. The quest is to improve health and not get injured.
I bike in two locations. Winter 8 months in Florida. Like the OP a house chosen near a 46 mile paved MUP. I use a road bike and can bike above 20 MPH on much of the MUP but not all of it. There is Inverness with many intersections, pedestrians, kids, dogs, cats. So I must go slow 10 - 15 MPH there.
But I do get my daily exercise there safely. I agree with the OP. MUP are great for what I do but not for speed biking. For that we must use roads and take our chances with erratic drivers. Roads in that area of Florida are not very bike safe for many reasons.
The other location is Wisconsin. The MUP's in WI are not paved. I have a special configured CX bike for that. One 23 mile long trail can be done in 90 Minutes. Lots of intersections and pot holes and branches fallen of trees. Few bikers and fewer pedestrians. Great exercise 4x per week for 46 miles.
Another trail goes for 100 miles one way from Reedsburg to Trempealeau. Few bikers and few pedestrians but chance of branches and wash outs with loose sand. Not safe to go much above 25 MPH for those reasons.
But good for exercise and fun.
I have done lots of road biking. It is challenging. I found it not possible to avoid all accidents. Road conditions, cars, bikers my skills or reaction time are an accident waiting to happen.
However a biker addicted to road biking will not like MUP biking. That is clear to me.
My fear of an accident overrides my desire for the challenge of road biking.
I am 72.