Engineers should blog publicly when they have something to say. Something useful for their colleagues. Engineers shouldn't waste time forcing themselves to blog instead of work just to push their career forward: frequently they just expose they don't have anything to say in extremely unreadable way. What a waste of time for everybody. Soft skills helps you grow as an engineer, it's true, but I think it's important to…
This is the issue. The latest generation has been told to constant work on their personal brand (ugh), and blogging is one way to do it. Though if we're working together, keeping the engineering wiki up-to-date is probably more helpful for the team than a some Medium fluff piece.
Don't get me wrong, there are some great blogs out there (e.g. A List Apart), and there's a benefit to a blog post reaching 100 people versus a Stackoverflow answer relevant for 10, but I think those that will blog well will do it naturally ("hey, people have been asking about this a lot, I should share a write up").
If everyone just contributed more by answering questions, or updating wikis, that'd would already be hugely beneficial, but to tell people sit down and write long-form is asking a lot. And JCDenton2052 also mentions the possibility of fucking up the signal-noise ratio.