I have 4 year old twins, one is ADHD and one is not. We spent a year working our way down the list of possible solutions before we got to the point where it was either medicate her or let her fail. No it wasn't just personality or low tolerance for an active kid.
The Therapist's office was set up as a diagnostic tool - 120 linear feet of shelf space, all at kid level, just CRAMMED with toys. My son would pick a toy, play for a bit, pick another toy, play for a bit, etc.
My daughter was a ferret on crystal meth, bouncing from point to point, rarely stopping long enough to even TOUCH THE TOY SHE WAS LOOKING AT.
She's on medication now (not ritalin, but I tend to forget the name of it) and she's still a very active 4 year old. But the meds take enough of the edge off her fidgets that she can actually stop and complete tasks if she wants to. We're still doing therapy to help her learn habits that will let her succeed in school and life.
When we got the diagnosis (two separate diagnoses, actually) I was dead set against medication - lucky for my daughter's therapist, she indicated that medication was a last resort or I would've walked out of her office then and there. But after a year of trying various non-medicinal treatments with zero success, we finally tried medication.
Anyone who says all ADHD diagnoses are just "kids being kids" needs to pull their head out.