There is no such thing as natural cadence. That's an idea invented to justify continuing to do what you already do.
When spinning was the fashion everybody spun. Everybody. History of polio and the bones to prove it - they spun. Multiple sclerosis - go ahead and spin. There is no one healthy who cannot spin. Tell yourself constantly some excuse for why you pedal slow and you are going to pedal slow.
Go to the gym and pump iron. If you lift the currently fashionable way it's sets of ten. Maybe less for the final set. On a bike unavoidably it is thousands and thousands of reps. Riding a bike like a weightlifter won't work. And you will never go fast. Current production bikes are already geared up to the sky. Top gear of 50x11 is accepted as normal. If you have no more than 60 rpm that means a top speed under 22mph. If you believe 70 rpm is spinning then you can do top speed of 25mph. Back when spinning was the norm - this is a long time ago - basically everyone who tried doing club rides quickly achieved the ability to complete a warmup at 20mph in a low restricted gear. Any who hung with it for a season were making 25mph and top gear was nothing like 50x11.