Nice article! Agree with slow leveling. In my current campaign I'm running the 5e version of Rappan Athuk. To give the old-school dungeon crawl experience, but still using 5e I do the following:
GP for XP. XP is earned by extracting gold and some milestones. Not by killing things. You kill things because they attack you, because you want their gold, because your characters think they are evil, etc. But there is no reason to turn the game into a slog of "clearing out the dungeon", though sometimes it makes sense to do that, to exert control over areas of the dungeon to have refuges you can retreat to.
This alone has done the most to make the game feel more old school.
The dungeon was designed based on old-school sensibilities and there are some save-or-die traps and creature attacks that are not common in 5e.
I do wish I made magic a bit more mysterious, but the dungeon itself can be pretty gonzo with magic. Also, I didn't want to deviate from 5e RAW too much and gimp identify, etc.