Also this usually works short-term because companies and people still have the infrastructure from previous government spending.
When that infrastructure inevitably crumbles because the taxes don't suffice to support it 10 years down the road, it's too late, the infrastructure needed to create new businesses will be missing, leading to a downward spiral for the economy.
It's not so much that the idea was simplified to push a political agenda: Arthur Laffer himself, when popularizing the concept (with the eponymous Laffer Curve[1]), used it as an argument against tax raise in the US.
So the big problem with economics is not so much that its results are being hijacked by politicians to push their agenda, it's that most of them (at least most of the prominent ones) are in fact pushing their ideologies through their publications.
“The basic concept was not new; Laffer himself notes antecedents in the writings of the 14th-century social philosopher Ibn Khaldun and others.”
IMO, it’s says less about economics than it does democracy. You can find many “think tanks” which are paid to create papers in support various ideologies. This doesn’t guarantee what they are saying is incorrect, but it does many they gloss over any inconvenient caveats.
Also, I’m assuming it’s unlikely the government has set the tax rate at the optimal rate to maximise revenue. But this assumption is probably dubious because even without explicit knowledge of the curve governments are probably pushed towards the optimal rate.
Austerity to the point of being able to pay down government debt is painful, that’s well known. Unchecked spending and unlimited growth in debt is however unsustainable.