I’m not sure I understand the last statement. Are you saying they should have one sensor, or three? The problem wasn’t two sensors - that’s normal redundancy. The problem was that MCAS was only tied in with one of the AOA sensors, and wasn’t aware when there was a disagreement in readings from the two sensors.
Three obviously - one would provide no redundancy, and having two with different readings would be bad as well since it would be unclear which provides a correct value
one of the dumber things Boeing did was having two angle of attack sensors; who the hell thought it was possible to have a quorum of two