Good news

So, the physically intelligent, strong people have an advantage when learning horse riding, I'll just give up now and take up fishing instead.

Whoa!

It does take a bit of time to learn how to use the muscles in your lower body. It does take a bit of time to get the strength. (Here I very strongly advocate Pilates.) But, if you can put the time into learning and strengthening your muscles, then I believe you can pull up ahead of the physically intelligent person.

The physically intelligent person applies the "feel". Whereas the less physically intelligent person applies the "science". Usually, once we understand the science, we stop doing things by feel. Why? Because science is more accurate. Science gives us better results.