Even though I have a CRT and NES, I bought one of the NES minis when they released.

I played some Mario Bros 3 and... I kept dying. Jumping too late led to running into holes and enemies. It was so bizarre, I couldn't believe how bad I'd gotten. Tried the next day, same deal.

Then I had a thought re delays. Pulled out my NES and hooked it up to the CRT and all that stopped

There was sufficient delay in the NES mini and modern TV it made a huge difference.

I'm sure I could retrain myself, but it was honestly stunned at how much of a difference it made