I agree about that - though one could say this is an issue we already have right now .
This might be something that could be solved via bonuses, though. I'd say failing 2/3 of the time is quite okay if the character is attempting something they just don't know a lot about, or if we are talking about a quick succession of tests in a stressful situation (-> combat) - for everything else, we have Skills and Talents, which may raise one type of character above all others according to their specialty ... such as, say, a Tech-Priest getting a huge bonus to working with technology.
"There are no particular special abilities associated with agents of the Adeptus Mechanicus, although all such characters receive +20% to any checks relating to using or disabling machinery, locks, etc."
- Inquisitor : Tech-Priests
I could even think about certain types of knowledge checks being an auto-success for the relevant classes, representing stuff they, by all rights, should know for sure - whereas others would have to roll on whether or not they could've picked up something about that topic. I feel this would further serve to differentiate character types and backgrounds from one another and diversify the game.