Gen Lesley McNair has a fair bit of blame (rightly or wrongly) heaped upon him; tank destroyer doctrine, training, repple-depple, poor chooser of field commanders. Each of these alleged "faults" seem to be decisions that could have gone either way.
So WI he wan't put in that position, is there anyone else who could have done the job that was available at the time? Would other Generals have made similar decisions; or would they have decided to go with heavy tanks, focus on combat rather than specialist training, implemented the replacement system better and chosen different field commanders?