That's a really bizarre statement to make. It doesn't match the game rules or reality in the remotest sense.
I disagree.
Given your standard compliment of murderous hobos that make up an adventuring party you have about 3-5 people with swords, axes, hammers, bows, fire bolts, and other implements of death and mayhem capable of killing / mortally wounding a "normal" person in a single stroke. On the other side you have a guard blocking a doorway with a military weapon of some sort.
What's faster and more reliable given the circumstance in a real world? Trying to wrestle him and extricate yourself cleanly or hitting him with a deadly weapon (which in the real world will basically incapacitate him in one shot)? Applying deadly force is -much- faster and more reliable in the real world. (It's just rather depraved in most circumstances.) It's even worse in a real-world scenario because while you're trying to bull-rush him said guard is going to be trying to resist by killing you with a sword / mace / ax / halberd!
What's faster and more reliable given the combat mechanics in 5E D&D? If he's standing in front of the door-way you need to move him 10' minimum to clear the area. That's going to be 2 successful bull-rush attempts against a character whose best stat is Strength. Depending on your party composition this could be a coin-flip effort at best, and a long-shot at worst. Pretty much regardless of party composition a round of just laying into the unfortunate fellow with your best attack options will be just as effective, if not more so. It'll just be far more violent.
Though, looking at some of the alternative proposals, grapple might be effective. Its' a 10' move, a successful grapple check, and 20' of movement spent to move him the remaining 10'. That could actually clear a doorway, though not a hallway. However if the guard has another friend at his back then all such methods are fruitless. You can't bull-rush backwards because the space behind him is occupied. You can't move his friend on the other side because the space in front of his is occupied. Knocking someone prone does not allow you to move through their 5' square area in combat. You're going to have to start dropping people to 0 HP at that point because that's the only mechanical solution that Combat section makes available.
Again, the real point here is that the
Combat section is full of mechanics for a
fight scene and escaping from guards in a castle is totally a
chase scene that calls for
Interaction pillar mechanics.
Marty Lund