I don't get why projects think a top-down straighten-up-and-fly-right edict is how you retain driveby contributors (I get why they do it, I don't get why they make that the primary/only change). That's a highly visible but overall small part of the barrier to entry. Online volunteer collaboration projects often assume anyone motivated to participate will self-train. Making the surface level language nicer only keeps people reading long enough to find out that they've walked into a busy office full of people working with tasks, process and goals they don't understand. Lots of the day-to-day in an office puts efficiency above approachability, and I don't think that's always wrong.
Surely WMF would have better results if they actually worked on the barrier to entry by explicitly adding to staffing(/recruiting volunteers) to onboard new editors. e.g. shepherd their work through onboarding-focused helpers until the newbie is ready to drop into the office proper. Use the failures of conversion to identify where there was a lack of handholding (and build a system for that), vs a lack of interest.