My point assumes people bias their learning towards their interests. That isn't an opinion, that's just human nature. That's not to say you
can't learn things that don't interest you, but if you aren't going to do it formally you certainly have to be driven by filling those gaps and most people aren't.
Learning to think outside the box and learning about specific specialties that you don't find interesting aren't even remotely the same thing. If you read what I wrote, you'll notice the example areas I gave. None of them were "thinking outside of the box", they were fields that didn't interest me.
The value they bring is that I learned a common language. I can talk to ML engineers or Compiler Engineers in a common language because I have experience in those fields that I wouldn't had I taken a different route. That isn't even remotely a requirement for my field. It's just useful for discussions with other people.
Maybe you'll spend hours and hours learning compiler design and implementation so you can have a friendly conversation with a colleague at lunch, but I'm not going to. Formal education forced that on me. That's been healthy for my professional networking, but that's about it. I still consider it useful, but had I skipped the CS degree I wouldn't do it. Nor would most people.