Stargate does mostly avoid that issue, but it falls down on the fact that the Goa'uld are ridiculously incompetent at both a strategic and tactical level. The most obvious being the fact that they never developed the iris that humans managed to develop almost immediately.
My theory is that they actually had an incentive not to be too competent. As long as their squabbling just gets a bunch of minions killed, it's fine. But suppose that one Goa'uld decided to fortify stargates, use a bunch of secret weapons simultaneously, and begin conquering in earnest. This guy would be wildly successful, for a while -- until the rest of the Goa'uld power structure decides to take him down.
It's well established that all Goa'uld have the vast knowledge required to pull miracles out of their hats at will. They can and will punish any defector who doesn't have a huge advantage. Just look at how they allied against Anubis, when he made his bid for supremacy.
The Goa'uld are not pathologically incompetent; they're just wary of being disruptive.
There is an episode which explicitly makes the point that the Goa'uld make very sure not to arm their minions with too much weaponry or tactical skill. The Goa'uld are very aware that they are not Gods and there isn't anything in particular preventing the Jaffa from overthrowing them.
