Not trying to defend Boeing overall here, but showing an explicit indication of an AoA sensor disagreement wouldn't magically have averted the two 737 MAX crashes. The basic cause of the crashes (apart from Boeing's dumb design decisions) was the pilots' failure to correctly execute the runaway stabilizer trim recovery procedure. Given that 737 MAX pilots didn't receive any training on MCAS, it's unlikely that the warning light would have greatly influenced their response to the situation.