I must admit, I don't know a terrible lot as far as 'facts' are concerned, about Monty.
But it seems to me, after many, many years studying and rehashing and listening to all kinds of accounts and studies of the man and his WWII exploits, he was said to be 'overly cautious'.
I think this may well be a reference to his 'preference' for only attacking when he out-numbered the enemy convincingly.
I think the main criticism, at least as far as Europe is concerned is that he was too slow and cautious in taking Caen, which was the linchpin in the Normandy campaign and certainly contributed greatly to the 'extended' breakout.
But then, 'Market Garden', according to a recent History Channel Doco, was quite ill-conceived also.
I'm not sure whether it was actually Monty who disregarded or 'shrugged' off the Dutch Underground reports that there was a crack German Panzer Division or 2 in and around Arnhem, but the responsibility for such glaring errors and misjudgements must lie with the CO of any Op.
All said and done, he was obviously an outstanding man and soldier to have been revered in the way he has been.