Learning to change the oil is different than rebuilding an engine. Just because something is easy doesn't mean its pointless. Pre-hopped kits teach you the second half of brewing. The next step is making the wort instead of buying it. And, there are unlimited ways to do that. I have a feeling that some people try to brew at a level that is too advanced for them, they end up with bad beer, and ditch brewing all together. You guys might as well make all your own furniture instead of buying it... because that is just pre-made crap.
I actually see it more of either making your own sauce, or buying it in a jar... While some really like the stuff in the jars, there's nothing like making your own. If I had a garden, or rather, WHEN I have a garden, I'll also work to use my own tomatoes in the sauce.
As for furniture and such you mentioned... IF I had the tools to do it right, I'd go for it. As for engines, it all depends on what it is in... Lawnmower, sure I'll give it a twirl (or small 2 stroke engines)... I've rebuilt air compressors pumps before.
For brewing, I did a few extract batches (NOT prehopped) adding hops when they were called for. Going with the prehopped brewing, to me, is just being lazy. Adding hops doesn't take all that much effort, nor is it difficult (for people with more than a few living brain cells left)...
Learning how to add different elements is important, but not difficult. Get a couple of extract (don't go lazy, add hops to the mix) brews under your belt, then a PM before going all grain.
DO keep really good notes on what you did for the brew, so that you can refer back to them when either things go where you don't expect, or you're looking for input on the brew. Just having someone taste it usually isn't enough. You might have aimed for one thing, but it ended up being something else. Once you start trying to formulate your own recipe's, get some brewing software to help out. It takes a LOT of the math off of you.
For all grain brewing, I'm enjoying the BIAB method (works well for PM batches too). Less hardware is needed (a really good thing in a small apartment) but you still get the benefits of going all grain.
Bottom line, while using some different methods can help you out, such as BIAB instead of making/using full on mash tuns, don't go too far into the 'idiot proof' methods. Unless you actually NEED those methods...
People that I know, that are also brewing all grain (for the most part, almost everyone does an occasional extract batch) tend to figure it will be an all-day affair. Or, at the very least, the entire afternoon, into the evening (depends on the start time and what you're brewing)...
If you can, find some people in your area to brew a couple of batches with, so that you can benefit from their experience. See what works for them, and then adapt it to your own style/personality...