Your definition of "straightforward" matches Demon's Souls perfectly. The game's design is quaint. It's not confusing, and it's not unfair. You are alive. You collect souls. If you die, you corpse run. You can die infinitely many times. Game progression is non-linear, linked by a hub world. That's the entirety of Demon's Souls.
It's not obtuse or complicated. It really isn't. As far as "streamlining" is concerned, I don't think the game's mechanics are complicated. There are no stats that are outside of typical RPG parlance. There are no unreliable or broken game mechanics.
The game IS, however, challenging, but again it is not unfair. You play the game and you learn to get better or you continually fail. The combat is slow enough and the enemies telegraph all of their attacks. There are items that regenerate your mana and your HP, and they stack.
Demon's Souls is not a game for people that want to run straight through a level whacking everything in sight. It punishes you when you die. So you have to try not to die. That's the entire mechanic. It's not made more or less difficult because of that. Change the mechanic, change the game. The game is already more than generous with offering numerous health items and shortcuts.
I will say that I really disagree with the idea that chess is more analogous to any modern game than to Demon's Souls. Unlike in chess, the majority of games lack any consequence for any actions taken by the player, offer infinitely many doevers for the simplest of tasks, and do not reward learning the game.
I'm all for making games accessible, but I do not think Demon's Souls is particularly inaccessible. It doesn't do anything tricky.