“It’s probably Matt Mercer’s fault.”
well a few things fix most of your list for for OSR. Start everyone at 10 hpts + con mod. , make all spells effects and damage character level so that if a fighter has a level as sorcerer at 12 level the spell is still worth casting. Get a few 3rd party GM tool books for encounter building and random encounters and your almost there.
Yeah I was going to suggest Shadowdark (of course) with some of the optional rules to make it less lethal.
But that still doesn't solve the shortage of "buttons to press" on the character sheet.