You assume that "gritty realism and desperation" should be forced upon the players artificially through the system, rather than the situations they are in during play. There is no need to "balance" a critical hit with a fumble.. that is not balance. Can players crit enemies? yes. Can enemies crit players? yes. *That* is balance(kind of).
In 5th, everyone gets to choose a different set of powers and abilities. Why should those abilities come at the cost of anything, other than "not getting the powers other classes get"?
Want to play hard mode? sure, go for it.. but there is no need to force it on everyone through punishing game mechanics.
5th edition, more than any prior edition has at least attempted to balance the game so that *all* classes are powerful in a different way, and all have appeal. Some abilities are out of scale, but it's reasonably close, for the most part.
You mention later "the original rules were made with the expectation that a random ability score generation would provide your options of what character to play. This limited the overall number of rangers, paladins, and even magic-users, but when you take that away everyone would be free to be one of the strongest classes."
This is terrible design. TERRIBLE. It's more punishment for bad rolls. Oh, you rolled poor enough not to be able to play a good class? Well, enjoy your low scores and substandard class, peasant!
Of course, I disagree entirely. People seemed to enjoy that design you call terrible well enough. If you want to make your campaign different, you were always welcome and encouraged to do so to your heart's content, but the original is the foundation forever. Everything else should be in the form and presentation of options, with a nod to the original design as "where all this comes from".