The question is, if you grant that a different design is better in a vacuum, how to weigh that against the benefits of existing familiarity.

That's easy. Would you rather have your coworkers working with an artificial handicap, or not?

Some people give regular users too little credit. A major reason they are such terrible users is because the software they are given is terrible.

Fix the software, and the users' ability is, to a measurable degree, fixed.

Existing familiarity is nothing compared with the daily additive benefits of better tools.