All this means is that we will inevitably reach a point where separate titles are used, and 'data scientist' will means about as much as 'engineer'.

We will distinguish 'machine learning specialist data scientist' from 'database specialist data scientist' just like we distinguish 'electrical engineer' from 'lab systems engineer', for example.

Then, we might have a term for generalists like 'data science technician'. And by then, the people who 'aren't really good at any aspect of it' and can't really function as generalists will be naturally sorted out because they can't really fit into any of those titles