Force equals one half mass times velocity squared. Apply that basic physics formula to pedal speed.
Pedal with exponents on your side.
90 or 100rpm is barely beginning to be spinning.
Does anyone here do a warmup? You should, any sport, and emphatically in cycling. Do that warmup at 110 and 120rpm. Easiest way to do that is to have a group that does that. Used to be every cycling club everywhere did exactly that. Those clubs are gone. Doing it on your own is harder. It can be done. It can be done faster.
Last summer I was 70 years old. Last summer I finally got to being able to go downhill smoothly on a fixed gear at 200rpm. Young people can spin much more easily. You believe you can't. Try believing you can.