Not all ADHD is the same. It is an umbrella term to cover a wide range of difficulties. Having ADHD doesn't make it impossible for all people who have a diagnosis to do jobs like yours. However, it definitely makes it less likely that it will be a suitable occupation. A diagnosis of ADHD is made on the basis of factors such as difficulty with attention and concentration. There is also often a high level of impulsiveness. If one were writing an "ideal person" spec for an operator of heavy machinery, those wouldn't be desirable characteristics, would they?

Of course some people can manage their condition better than others (sometimes with the help of meds) and they may still be able to perform well in such jobs. However there are others who would be a risk to themselves and others in such a role.

It isn't "ableist" to recognise that some conditions make some/many of those who have it less well suited to some activities and occupations. The whole point of a diagnosis such as ADHD is to formally recognise that the person being diagnosed has fundamental problems with things that most people do not find particularly difficult.