Fort wars is a gamemode with huge potential, but almost always piss poor execution.
Most people just throw a blank/sparse map, and make people build their own individual forts, while combat is happening.
It just turns into a mess of people screaming "OMG I WAS BUILDING", people just dming with no fort involvements, arbitrary alliances, etc
Even worse is when they're able to spawn whatever weapons/events they want
The best (admittedly I haven't played them often or in a while) fort wars I played was split into two teams, the map just a couple (very large) floating platforms with a gap between them, and the match split into two phases: a build phase, and a combat phase.