Yeah, I’m at an interesting crossroads, because the principles are what I’m interested in more than the specific mechanics and design quirks… But also I really like the aesthetic of D&D, and I feel like that often gets lost when focusing on principles over specific mechanics.
I may be repeating myself, but maybe I can clarify a bit on how the games I mentioned fall in line with these things.
OSE is straight-up B/X D&D. It retains all the mechanics and quirks of B/X, including race-as-class, but it also has optional rules for making race and class separate in the advanced rules. B/X is pretty tightly oriented around dungeon crawl procedures.
Black Hack is more about OSR principles rather than being a faithful D&D clone. It still uses the six attributes and a d20, with a roll-under-attribute mechanic. It orients those principles more towards streamlining the game with four classes (Warrior, Thief, Cleric, Wizard), rules for Backgrounds (which would be a good place to include Race), and simple dungeon-crawling rules.
WWN is a bit of a hybrid beast. There is a lot of D&D in there (Six Attributes plus d20 rolls for combat), but also some Traveller (2d6+ability skill checks) and 3e/True 20 (skills, builds, warrior/adept/expert/adventurer classes, feat-talents, etc.), but it's good for running open world sandbox campaigns that also include evolving factions. Characters are still fragile, but there are also rules for more heroic characters should the group prefer that.
Index Card RPG is classless, but it has races (usually simple stat bonuses). It's pretty focused on light, simple, quick gameplay that's about acquiring loot for improving your character (think video games). For example, ICRPG uses a room DC, which makes everything in the room use the same DC, which can be adjusted for Easy (-3 DC) or Hard (+3 DC).
There is also
@Sacrosanct's
Chromatic Dungeons (there is also an 0.90 basic rules version) that updates old school D&D for more inclusive sensibilities. Honestly, I feel like a fool for not mentioning this game before. Do yourself a favor and check this game out!