Are you sure you've actually used the higher refresh rate? It might not be enabled by default. I'd be surprised if you can't tell the difference comparing 60hz to 120hz back to back.

Well, I have an M1 Pro MBP so I'm pretty sure.

edit: ok, I've tried toggling ProMotion on and off, and I can see it. However, I still think the improvement is marginal.

I use an M1 Macbook Pro for work and an M2 Macbook Air for home, and I basically don’t see any major difference.