Well, technically the failures of MCAS should be unproblematic, as the stabilizer runaway protocol is well trained for any 737 pilot and would cope with a MCAS

Well, technically the failures of MCAS should be unproblematic, as the stabilizer runaway protocol is well trained for any 737 pilot and would cope with a MCAS misfunction. The problem is: in the two crashes the pilots either completely failed to follow the protocol (Lion Air) or to late and failed to recover (Ethiopian Airlines).