Yes, the human eye can see more than 60, 120, 144, 240, and so on… but if you own a 144hz monitor, you will never be able to jump the same amount of smoothness with an upgrade to an even higher refresh rate as you felt when upgrading from 60hz. Its not placebo, you will feel it… but less and less so with every upgrade.
X-axis: Refresh rate (Hz)
Y-axis: Frame time (ms)
Equation: y=1000/x
https://www.desmos.com/calculator/kzjhpeappd
For a crude comparison, you can use values A (monitor refresh rate to upgrade from) and B (monitor refresh rate to upgrade to) and the above equation will tell you a value that is the same percieved smoothness difference, but between a lower refresh rate and the monitor refresh rate to upgrade to. Apologies if that isn't clear.
Basically, if you set A to 144 and B to 240, then the percieved smoothness difference from 144 to 240 should be like going from 103 to 144, and you can then compare that amount of difference with the 144 refresh rate and not have to buy 240 to get an idea of how much difference there will be. This is not at all a perfect way to compare, but its much better than thinking 2x the refresh rate will mean 2x the smoothness.