Laffer Curve too simple
Talking about the shape of the curve is pointless since all it does is plot a tax rate, the video mentions the top rate, vs. government revenue while ignoring the fact that the tax rate varies with income. Putting it into perspective, it's perfectly possible for the top tier to be 99% but the question becomes one of where it kicks in.
A lot of people like to talk about top historical rates being much higher like "Oh back in 1936 the top rate was 79% and folks got along just fine." What they don't say is that rate applied to folks who made $5,000,000 in 1936. Today that income would be equal to $82.5M or, for a 40 hour work week, a bit over $39,000/hr in the middle of the depression. I can't but wonder how many people were paying this rate.
Compare more common incomes today and adjust backward for inflation to 1936 tax rates and folks making $50k pay 4%, $75k is 8%, $100k is 9%, $200k is 12%, $500k pays 23% and working up to a modern $1M makes the 39% bracket. Does anyone know anyone earning $100k and being in the 9% bracket? That's 9% U.S. Federal income tax, not 9% California income tax.
And there's the rub, the tax brackets don't keep pace with inflation. Folks are paying a lot more in taxes for the same net pay. It kind of makes the Laffer Curve a bit laughable if you just plot the top tier tax rate if it doesn't effect anyone.