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Thinking on it now, I realize it's not that we don't want "More Armor, More Guns, More Engines"
We can still try to have armor and shields as thick as Dorn's ships.
Harder and bigger guns straight from the dreams of Techpriests.
Powerful engines to move our ships at pace.
All of these things should come naturally with increases in size and scale of our fleet. Except the sensors. You can't just strap on more sensors like you would heavier armor, you need to come up with a more powerful and better design, something a tech specialist like us would perform well at.
Even the Emperor's mighty ship would become little more than an (admittedly very tanky) giant golden bunker if its sensors/psykers are disabled and it cannot chase or return fire on vessels so many light minutes that they are practically invisible on the black void to any form of visual rangefinder.
"Acquire the Enemy, See the Enemy, Hit the Enemy" is a full 1/2 of the survivability chart, all of which no amount of guns or armor will help, but better sensors are needed.