The problem, as I see it, is people just have very subjective memories. So, like people claiming that the G modules were infiltration missions, like actually viable ones. DMs either just run things in a ridiculous way (the other guards 40' away never hear the bloody melee, and the front gate guards mysteriously spend 4 rounds fighting before one makes a dash for the alarm bell). That is remembered as "you can get past this even if you fail some checks." Even if the party does NOT actually fail any, the memory is "well, maybe we could have and still made it" without actually testing that.
Beyond that, maybe you CAN get past, if you selected the right spells, because spells always solve everything. This is why D&D has gotten away with this stuff for decades, because the truth is Invisibility, Silence, Charm, Magic Missile, etc. is really the logical infiltration tactics. Relying on skills is just basically a 'spell saver', you can try it first, but make sure to be ready with the magic when it goes bad. 5e has made this MUCH more effective too, since you don't need to exactly memorize the precise spells you need in the precise quantity.