My cadence has improved over the past 60 years. I usually average around 88 on a long hard ride. My best cadence for power intervals is about 96, 78 to mid 80s for LT intervals.

Try this: Once a week, get on your bike and spin as fast as possible without working really hard. Try for 115-120 cadence. You might need to use the granny ring. So what. Use just enough gear that your legs don't just flop around and you keep a tight chain the whole time. Every week, add 5 minutes to this interval until you get up to around 1/2 hour. Do this most of the year. Keeps you flexible. It's easier on rollers than on the road because of stop signs, hills, etc.

Relax your toes, keep your feet flat, don't "ankle," try to keep a layer of air between your foot and the sole of your shoe. You might do better holding the bar tops. Keep your back straight and head up.