I largely agree, but setting up mail server these days is way, way, way more complex than 10 years ago. It’s not people losing skills, it’s technology itself becoming overly complex.
I disagree. It's a little more complicated (due to SPF/DKIM/DMARC), and that's annoying. However, I have set up multiple mail servers in the past 10 years, and I don't find the complexity to have increased that much. It is more complex, but not "way, way, way more complex".