Well I wouldn’t go to that extreme. Classic horde is its own different beast. But with a competent engineer and people not being stupid, you can walk through Advanced at any level, really. Especially if the higher damage modifier isn’t picked.
What causes people to lose at less than Insane isn’t low leveled characters. It’s bad/ignorant players. Guys who frequently run out of position, or buy their own stuff instead of letting the engineer, or worse, an engineer who doesn’t know how to setup. A marksman who can’t snipe. A Jack who barely uses the forge built for him. An infiltrator who keeps dying on the other end of the map. That sort of stuff.