Barbara has the tech to see what Cass sees. She's had it since way back when in Birds of Prey. Cass not being able to read should have been dealt with better, but it's a handicap with a technological work around.
Saying she shouldn't be able to fight crime because she can't read Riddler's stuff is like saying Barbara shouldn't be able to fight crime because she can't leap across rooftops. The Bat-family has the means to adapt, they just choose not to do so.