It isn't as black or white as you are trying to paint it. It isn't ALL the managers fault or NONE of the managers fault in either the case of AVB or TS. Some of the responsibility for the poor displays must lie with the players whoever the manager is.
However, there is a big BUT coming. AVB CHOSE these players, spunked over £100m on them, had 18 months to sort out tactics and a playing style, had the benefit of two pre-seasons and two foreign tours to get this bedded in and presided over some of the most turgid displays and utter humiliations in recent memory.
TS has had a squad he inherited, many disillusioned and dispirited players, a team which couldn't score for love nor money and were conceding hatfuls, a humongous injury list in the middle of a season where every game is important. Sure he has made mistakes (and I have criticized him when he has done so IMO), but you do see the difference, don't you?