This is why they do not like ANYONE fucking with technology, because it is so rare to find anything that just works it is critical it not be compromised. That, and they do not have the actual knowledge to fuck with it intelligently, just through experimentation, which inevitably leads to slaughter. Pressing buttons to see what works is fine in a 21st century computer, but it is a very stupid thing to do at the helm of a 410th century starship with the destructive power to end solar systems. The entire knowledge base of humanity was lost. Not forgotten, but outright lost. Everything at all, poof. Nobody knows anything because the Fall fucked everything up and the Heresy double-fucked it. To rebuild the theoretical framework needed to design new technologies that don't kill everyone near them would require starting from the ground up. They don't have the time, and they never have.
This gets on to the point of war and what it does to technology. Someone will parrot that it makes it go much faster. Yes, it makes practical applications of technology go much faster. It also utterly stops all research on the scientific theories behind those technologies. This means that when war chugs along for a decade or two things get done. It means when it goes on too long you run out of theories to turn into technologies, and then you run out of technologies to apply. You stagnate. When you have been fighting in a war for survival in a drastically overextended empire, this is what happens. You are desperate for any extra materiel that can possibly be produced. Half your entire fucking military might went rogue, smashed the half that stayed, leaving you with the tattered shreds of a war machine to keep hold of an empire that was reaching straining point with an army far larger. There is no time for the sort of applied research programs that took Man twenty five thousand years to develop, in a time of unprecedented growth and prosperity.