Meanwhile there's a world of threats out there that could come in at any minute and destroy their community. Rick's seen it happen and that's what he's focused on right now.
Rick cannot know that. The ZA hit the
entire world, leaving no area truly safe. It has been repeatedly demonstrated that human could not survive--
and continue to build a shielded community without direct contact with walkers. Even the Greene farm had enough walkers (beyond Hershel's relatives) to collect in a barn, and his farm was fairly isolated. In other words, the walker threat is everywhere.
Alexandria was not isolated. In a heavily populated area, all humans could not leave, so-called rescue centers (military, school, etc.) would be quickly overrun, and (as seen time and again) highways would be blocked with a sea of abandoned cars, and wrecked areas due to conflict.
That means innumerable groups would still be in the area, & many more turning into walkers--which Deanna's group--
all while trying to establish the ASZ--had to handle. Is there any logic in the assumption that Deanna's group had the luxury of time to just gather supplies, find, transport and erect walls, etc. without conflicts with legions of walkers?
In the Noah death episode, we see the building and surrounding area swarming with walkers, and it was not too far away from the ASZ.
Bottom line, no one could build the ASZ without constant run-ins with walkers, and roaming humans. Rick is wrong.
If this other group can take out a several-inches thick brick-and-mortar wall, then Alexandria and their shitty wall made of the sides of a steel building aren't going to do shit.
See the reply above. I'll add this, think about your comment: if you think the steel siding is not so great a wall for protection, do you consider that they have
other reasons for not being a defensive as Rick's group? Such as a connection to a nearby group?
So, the larger premise of Rick's point is correct. The Alexandrians need to toughen up a bit. And, yeah, he's got a boner for Jessie, but that doesn't undo the fact that she's being abused by her husband and the man likely abuses, or has abused, her son too. That's something Deanna and the Alexandrians shouldn't be so willing to just gloss-over and ignore simply because Pete's a doctor. Again, how good and reliable of a doctor can he be if he's hammered all of the time?
About your
"hammered all of the time," line, we do not know how his days were spent pre-debut. It could be occasional, slowly building, etc. Still, if his drinking was such a problem, then why would Rick's group trust leaving Tara in his care? No matter how critical she was, a true drunk could miss treating something requiring the most stead of mind and hand, or, if in a drunken, pissy mood, just blow off the patient.
Lose a surgeon in the ZA world and what do you have? Civil War-esque field butchery (Hershel's leg), or death.
So, the only thing they need is someone with some good first-aid knowledge and knowledge on pharmaceuticals to try and give an injured person as many chances as possible. It's a crummy world, but someone likely can learn that information by raiding a medical school and getting some text books or something.
A first aid training and pills cannot treat a woman with complications from pregnancy, or someone with serious head trauma. As noted above, lose a surgeon in the ZA world and what do you have? Civil War-esque field butchery, and more death.
But, really, I'm not sure there's anything I can say to make you change your mind. Your Rick-Hate has always been strong.
No one hates Rick, but i'm not the first of many WD fans to observe that he's been turned into a predatory asshole pushing everyone away.
...and about that hate business...that cannot even touch the torch and pitchfork death squads who attack Carol every week. You would think she was Gareth from some of the exaggerated comments i've heard.

No kidding!
There will be a long, emotional process where Rick says his goodbyes, everyone's misty eyed. As Rick's about to exit the gates, THAT's when the Wolves attack, and Janeway has to plead with Rick to stay and fight for them. And someone will die. Most likely Eugene, since he's not as useless anymore.
Begging Rick to stay would be too predictable. There has to be consequences for Rick (now in Carol's S4 position), and new decisions / paths for the others. The plot stagnates (new villain or no new villain) if the heroes just crawl back to their same pecking order. If the big deaths of this season (and there may be more to come when all is said and done with S5) carry any meaning, then the characters need to seek a world they have not known since the start of the ZA: a world that is as close to normal as possible.
Going back to the same old methods is not progression for the characters.