Well, as most people don't read the manuals anymore (I fail at this) and are quick to give up the moment anything confuses them
This is where I think you're actually wrong, though. I think you're way underestimating even casual players. Casual players -- more than anybody else -- want to pick up and play right off the bat.
I really think most casual players will deal with initial confusion far better than dealing with an annoying tutorial. Initial confusion can be fun. Tutorials just usually are not fun at all.
And besides, if you can't figure the game out without a tutorial, something is WRONG with the game. You can start a game off being extremely simple and continually add complexity as time goes along. Those expansions in games like Super Metroid were not
only for the "oh wow, that's so cool and unexpected" moments; they also ensured that the game started simply and ended with more complexity.
I've never had a problem with tutorials and I don't understand why someone would return a multiple hour long game because of a 5-10min long tutorial.
Because they'll never actually GET to the game.
Not trying to defend tutorials but clearly there is a difference between reading about how things work and actually trying to do them
You'd have to, ya know, play the game to do them. Since when are you supposed to be able to do everything 100% correctly the first time?
In this day and age, I'd imagine that most people would get to a pitfall (i.e., hole) in Super Mario Bros and demand a tutorial on how to cross it. Do people really want the game to pause when you come up on a pitfall and have a balloon window appear that says, "Ruh oh! Looks like you've stumbled upon a pitfall! Here, you'll need to have Mario run (hold down the B Button) and jump at the right moment! We're going to take you out of the game temporarily so you can get in a few practice jumps!"
Have we really been that reduced as a society? That we can't POSSIBLY have failure on first attempt?