This is wildly inaccurate and ignorant, and basically perfectly sums up why the problem isn't being treated effectively.
1) The drugs aren't serious and life changing and they don't alter core aspects of your personality. People seem to confuse the effects of mild stimulants like ritalin and adderall with the effects of powerful antidepressants like prozac (I blame South Park, et al). Stimulants can have negative side effects, but they're more along the lines of what you'd expect from too much coffee: loss of appetite, hyperalertness and sleep problems, in extreme cases twitchiness and cardiovascular problems. These are well-understood, and any doctor would adjust/halt the drug if they got worrying. In terms of personality, the person is just getting a boost to their deficient executive function. The net result could be that they're less likely to do things impulsively, but not that they're less likely to do things, period.
2) I'm all for letting children think how they're going to think, and agree that our education system is far too constraining and cookie-cutter. But there's a huge and meaningful difference between "let kids think how they want" and "don't treat problems that are preventing kids from thinking lucidly". Some excellent research has shown that even if parents and teachers bend over backwards to facilitate kids with ADHD, unless they get some kind of treatment (and medication is both much more effective and far less expensive than behavioral therapy) they're still going to struggle.
So what people who advocate "let (kids) think the way they NATURALLY think" are effectively saying is "let some non-negligible fraction of kids have a dramatically lower chance of success and happiness in life rather than acknowledge that they have a disorder and treat it".