My understanding is every time a "Laffer curve inspired" tax cut has happened in practise, tax revenues have indeed gone down.[1]
The thing about the Laffer curve idea that I don't understand is the curve doesn't need to be continuous. Say we accept at a tax rate of 100% you get no marginal benefit from working so no-one will work and the tax take will go to zero, at a tax rate of 100%-epsilon you still get (small) additional marginal utility for each additional dollar earned, so it's still in your interests to work. So it's literally only at a tax rate of 100% that the Laffer concept would make the tax take go to zero.
[1] https://medium.com/junior-economist/the-laffer-curve-6bb2833...
"In practice, the Laffer Curve has not provided the dual benefits of lower taxes and higher revenue. In fact, every US tax cut since 1965 has been followed with a sharp decrease in tax revenue, while every increase in taxes has led to an increase in government tax revenue."