3) Due to reason 1 (npc's are impressed at everything we do) the "feats" we have done isn't akin to getting a masters, more like surviving a war having done 10 valiant deeds and won. Why is this important? A masters or phd HAS to take years. But what our characters have their reputations risen due to won battles, which can literally happen within a span of 6 months or so (yes, you can get a job's quests done in a few days. But that's probably a few months in eozerea time). Plus, to the NPC's we did all this on our first try. But in reality, we've died a dozen times, sometimes, to beat a fight. If I saw an immortal (but didn't know [s]he was) slaughtered an entire army by him/herself, I'd praise his name too.
TLDR: The "mastery" and "feats" we do in game aren't as insurmountable as the npc's seem to think.
4)If you (you, in the general term. Not you, Kyah, specifically) play this game like a casual player (no power levels, no LS giving you items to hasten crafting skills. No getting ran through dungeons to complete quests by way more experienced and better geared people. Walkthroughs to tell you exactly what you need to do, but figuring it yourself instead, etc.), you wouldn't have had time to get all your jobs and crafts to 50 and complete all the quests. My wife and I only were able to play on and off and the most I've gotten done is drg,whm and blm to 50. (I did get ran through a lot of blm's quest). Cooking to 30+. Harvesting and mining to 45+ (and a few subjobs). She only got mnk to 50, all crafts except cooking and alchemy to 43. The people that got all their jobs and crafts and stuff to 50 either spend a lot of rl time or got a lot of help (or a mixture of the two). Again, I wouldn't blame the job system for this.
TLDR: Some players spent a lot of time or got a lot of help or both.
So none of the above points by themselves explain why all this seems "unrealistic". But when put together (some bars lowered and other rates of things increased), you can see how these things, although unrealistic to normal people, is still in the realm of possibility, even in the real world, if certain criteria are met. None of which, are the job system.