I think some article in PCGamer back in the day quoted Warren Spector regarding Deus Ex, and its complexities, as him regularly going into his office and sitting down to figuratively bang his head on the desk while asking why they make things so hard on themselves over and over.
The decision that the player should be able to win via multiple paths, be it sneaking, gunplay, or something else entirely, really made it a beast to work on.
Damn it, there is a whole sub-section of one of the maps were you can encounter mobs you normally only encounter towards the later end of the game. And you do this by following up on a missing person and finding a way into the sewers.
That said, i keep coming back to a quote found over at Filfre, where one of the people that worked on the early Lucasarts (still Lucasfilms Games back then) games muses over how game developers have a bad habit of getting distracted by new toys.
Meaning that whenever some new hardware came along that allowed more of something, more colors, more sprites, more anything, they would invariably churn out a mass of shallow action games or similar to show of how many sprites or colors they can make the hardware push. Effectively the industry is rolled back by several years of development practice (and i dare say something similar happened with mobile tech when the iPhone released).
And it may well be that as we keep having AMD and Nvivida push out new GPUs, that we are stuck in a rut of continually colorful and well rendered but bland games.
Never mind that with the gamepad being the more likely input device, many interfaces are hampered (Deus Ex inventory tetris anyone?).