If youn put me in the starting lineup for an MLB team, I'd strike out every single at bat for the entire season, and it's wouldn't be a "mistake" on my part; I'm just fundamentally incapable of doing the job.

A mistake is something that happens when someone capable of doing the job well happens to not do it well in a specific instance (without ill intent, of course). If it happens often enough, the question should be whether it's a mistake or if they're not able (or not willing) to do the job as expected. I don't know that this is what's happening here, but the issues seem to be large and frequent enough to at least warrant a discussion.