This doesn't even make sense. How do you know what the network links or the other bottlenecks are like? There are a grandiose number of assumptions being made here.
Obviously it's possible to build, for example, a machine with 2 cores, a 10Gbps network link, and a single HDD that would falsify my statement.
Even if you somehow get everyone to follow best-practices, you most likely still won't get to saturate the network on "minimal hardware". The number of client connections and requests per second will likely saturate your "minimal CPU".
It's true that minimal hardware on Kafka can saturate the network, but this mostly happens in low-digit client scenarios. In practice, orgs pushing serious data have serious client counts.