Needless to say, their highly boasted walls are crap imho. The prison fence may have been lesser, but the actual prison walls were monumentally better. Plus, the prison fence, though it fell eventually, still had the advantage of allowing for easier handling of walker populations. Alexandria's wall requires elevated positions to deal with growing groups, (Which I've not seen) and the expenditure of munitions, or you actually have to go out there & handle it
The only advantage Alexandria's wall has is that it conceals their community. I think that's what has been their blessing. Nothing living or otherwise knows they're in there......... Yet. Except these twits she exiled. It's fair to start assuming they are wholly inexperienced at dealing with what's become of the world of man. Frankly, Rick's group has now seen the some of the hardest remains of a brutal condition
That's why Rick sounds exasperated when he asked "So you've been behind these walls the entire time?". The vast majority of them don't know squat & aren't prepared at all, & they've woefully underestimated Rick's group, because of a superficial vetting. They saw 8 haggard guys, 6 little women, a boy & a baby, in the worst condition they've ever been & never once considered that apart from a couple of them, that group is a damn roving death squad. The 3 dozen guns should've been a tipoff. I'd put Carl's metal higher than Aiden's, ROTC be damned
That's the best & worst thing our group has going for it. It doesn't look as tough as it actually is, especially now. Carol knows it. That's why she's playing possum. She knows these people have no idea what they've bargained for. If they tip their hand too soon, it will fall apart.