I've always assumed stimulants make smart people sharper, but it's the opposite.
In a 2023 study, people on Ritalin, modafinil and dextroamphetamine worked harder on a complex problem, but the quality of their solutions dropped.
Plenty of people report feeling like their IQ drops by few points on e.g. modafinil.
I'd say these might feel useful for tedious work you absolutely disdain, but probably not for creativity.