This is...not simple. I agree that container networking is not all that much different from other Linux networking, but that doesn't make it simple. A lot of application developers are switching to working with containers and haven't historically had to do any manual network configuration. It's all new to them. Linux networking conventions change every few years and simplying keeping up with the basics is a chore. netplan is the current flavor of the week but it's still new to plenty of people who've never had to worry about anything more than auto-configured DHCP or cloud-provider-default VPS networking.

There are also important security considerations with container networking. Docker, by default, punches massive holes through your firewall in non-obvious ways. People don't realize that with a default Docker configuration, containers are ignoring any normal firewall rules you may have setup with iptables or ufw. Locking that down is only easy if you already know iptables well, and even if you do, managing it is a pain.

The article doesn't touch on Kubernetes, but that's a whole other can of worms. You have to pick a CNI and manually configure it; DNS doesn't just magically work; default CIDR allocations often conflict with existing networks; load balancer ingress for a development/single-host/non-cloud environment is a horror show.

This is a good and helpful article, but container networking is not simple by any stretch.