Yes, I do not agree with this kind of advice.

A warning that hosting e-mail yourself can be difficult, is very useful, but the suggestion that you should not do such a thing is not.

I have been hosting my own e-mail since 2004, for more than 2 decades and I do not intend to ever give up on this.

The cost of hosting my e-mail has been absolutely negligible and for most of these 22 years, the time spent managing my (FreeBSD) e-mail server has also been completely negligible (perhaps an hour or two per year, on average).

A good mini-PC, e.g. an ASUS NUC, with a negligible power consumption when it is operated 24/7, is completely sufficient for hosting everything that might be needed for Internet access, e.g. router, firewall, NAT, NTP server, dual DNS servers, DNS proxy and cache, SMTP server, POP3/IMAP server, HTTPS server, Web proxy and cache, DHCP server for the internal network, etc. On a mini-PC that does not come with enough Ethernet ports for your needs it is easy to add many more ports on USB.

It is true that a few years ago I have encountered enough problems with stupid e-mail servers configured to automatically reject as spam anything that does not come from a huge company like Google or Microsoft, but thankfully during the last couple of years such cases have become more rare, not more frequent.