This is not true, if you run Debian / CentOS7 / Ubuntu, out of the box the settings are good. The thing you don't want to do is start to modify the network stack by reading random blogs.
I agree these are good defaults, but they are not meant to work well for all kinds of workloads. And yes, if things are working for you they way they are, that's okay; there's no need to change anything.
On the other hand, I personally don't know anyone who runs production servers of any kind on top of unmodified Linux distros.
You are so, so so lucky... lol. I say that as someone who has come across a desktop CentOS install on a server on multiple occasions, complete with running x-org and like 3-4 desktop environments to choose from, along with ALL of the extras. KDE office apps, Gnome's office apps, etc... HORRIBLE.
Really? The distributions might work for the average site but high-load always requires tuning from the defaults on even the latest distros.