* In the real world, servers misbehave, like, a lot, so you have to deal with that fact. All assumptions about network robustness in particular will be proven wrong on a long enough timeline.
* Leader election in a world without a robust network is an exercise in managing acceptable failure tolerances. Every application has a notion of acceptable failure rates or acceptable downtime. Discovering that is a non-trivial effort.
Jeff Dean and others at Google famously came to the conclusion that it was ok for some parts of the Gmail service to be down for limited periods of time. Accepting that all self-healing/robust systems will eventually degrade and have to be restored is the first step in building something manageable. The AXD301 is the most robust system ever built by humans to my knowledge (I think it did 20 years of uptime in production). Most other systems will fail long before that. Managing systems as they fail is an art, particularly as all systems operate in a degraded state.
In short, in a lab environment networks function really well. In the real world, it's a jungle. Plan accordingly.