Research has found those who use medications such as Ritalin without having conditions such as ADHD actually reduce their mental performance on cognitive tasks.
The interesting point was that the meds did sometimes did have an effect, but often it was more about focusing energy in the wrong direction.
Presumably the ratio of benefit to detriment is worse if you don’t have ADHD to correct, but if you have ADHD it can still give you more focus in the wrong directions. It help deal with staying focused, but you absolutely have to still put in something effort to force that focus where you want it. It’s an imperfect, but still wildly helpful tool.