Here's my take on it:
1) AR's are dime a dozen. I suspect, 99% of AR's never had more than 1000 rounds through them. Unless your navy friend is planning to compete, hunt or train a lot, getting the most reliable(more on that later) or more fancy/expensive is just money wasted. Reliability for something that may be used defensively is not money wasted. Omnidex controls, fancy charge handles, pretty handguards: all these items add to the price but don't make an already great rifle any better.
2) AR was designed to be cheap to make and it is. No, it was designed to be easy to repair and maintain. Thankfully they can also be fairly cheap now due to the proliferation. Any brand that tries to sell you a "fancy" AR is selling you the brand, not the rifle. Some, sure. But far from “any”. There are legitimate engineering, materials, and feature advances going on. Whether they are worth increased price is up to the buyer, but it’s often more than just brand and they will often filter down to lower priced ARs over time. It's like Toyota Highlander and Lexus RX: The same car but one has more "bling" and the name(Lexus). Both will get you places for many years to come. You can even get down the "cheap" brand path and get a KIA and that car will work just fine. As with cars, there are certain parts you don't want to cheap out on. For ARs, barrel and BCG are the only two parts where quality matters, and the rest is just fluff. Oh god no. BCG and barrel are very important, but lots of other parts are important too. Get a flimsy handguard and you can get accuracy issues by hitting the gas block. Crappy buffer springs can lead to unreliable behavior or a short life span for the spring. Cheap gas blocks can be very leaky and result in very inefficient gas systems. Cheap gas tubes can lead to unreliable cycling due to a bulb that is too long. Cheap lowers can cause trigger pins to walk. Cheap charging handles will break if you need to kick start the gun due to a stuck case. Etc etc.
3) What makes ARs finicky is the gas system. There are three sizes: Rifle, Mid, and Carbine. Carbine is the most unreliable of the three and I wouldn't bother with it if you want a simple rifle that shoots any ammo. The most reliable is Rifle followed closely by Mid. A cheap $400 Bear Creek AR with Rifle gas system will eat any ammo whereas a $3000 LaRue with Carbine gas system will be picky about ammo. Also, AR was designed for a 20" barrel. The close you are to that, the better you are. 18" w/Rifle gas system, or 16" with Mid-length gas system are probably your best bets. No no no no. First, there are more than just those three gas system lengths. Second, the carbine length is not finicky in the least. The last time carbine length was finicky was back in Vietnam when they tried to use a 10.5” barrel on the XM177 before going to 11.5”. Carbine gas systems are usually slightly “harsher” on the shooter, but are extremely reliable and not finicky. Are you really trying to say that the M4 and M4A1 is finicky? Yes, the AR was designed for 20”… like 60 years ago. We have come a long way since then.
4) Money you waste on brand recognition is the money you won't have for ammo and training. I’ll take this as “buying a more expensive AR” rather than buying the brand. It is not a waste when you get to a course and your gun craps the bed and you realize you need to get something better. Then you’ve wasted time at the course and wasted money on a cheapo AR that you now want to replace or at least upgrade with more durable components. At courses, the highest number of malfunctions come from people with low tier ARs and those who do home builds with cheap parts or when they don’t know what they’re doing.
My suggestion: get the cheapest 18" AR with as close to the original design and shoot the snot out of it until it's broken-in and reliable AF. That is so limiting and completely unnecessary at this time. Hell, even 20 years go. Are you really advocating the guy get an 18” AR with rifle receiver extensions to use for home defense?