The E6B doesn't tell you anything you woulndn't know from training on a single airframe for 6 months to a year straight...
You look at the fuel dial on a P-51 and you'd know exactly how much gas that is in gallons based on experience and math (% of total).
But jump around plane to plane, a hundred different options in this game, and you cannot remember ALL the different max fuel loads of EVERY plane in the game.
The rest of it is basic math... "I know at this rpm and this boost my manual says this many GPH are consumed, look at my fuel and it's got 50% on the dial, that means X gallons, so I know this many gallons times this many GPH means I have 10 minutes left at this setting"
It's really not that hard, it's just that we don't have that kind of thing permanently ingrained into our minds. So the E6B just fills in some of the blanks and does some basic math. Outside of the GPH and fuel remaining, the rest of it isn't important to me. I do my own mental estimation of time left and duration, etc.
But without memorizing engine settings for a year, a pilot manual to constantly refer to, and without knowing at a glance (from memory and experience) how many gallons I have left, I need the E6B.
There's nothing cheating about it. It's not a crutch in the way the OP describes it. Not for anybody that's moved beyond the "newbie" status, I'd wager.