projects beyond a certain size in a large org imply things which are very different - people, networking, money, regulations, politics, business, security etc all things which don’t look spectacular when you have three people, but become very important and much harder with hundreds of people.

So career development really means ‘learning a completely different skillset which is not technical’

That's a good way to put it and is something I've often thought as well, although not just in the technical realm. I think of it as "doing a different job". You used to be a teacher but now you're the principal; you used to hammer in nails but now you direct the construction crew; you used to be writing software but now you manage other people who write software; etc.

Personally I'd struggle to consider that "development" for my own life, since it often amounts to no longer doing the job I like and instead watching other people do it. I can understand how adding new skills is positive, though.