I am one of those that I "get" how "Basic" or B/X and BECMI are derived from 0e, they aren't 0e because 0e was still race and class separate and while rules as written didn't allow for a dwarf wizard, for example, the baked in race as class concept didn't hamstring things so playing a dwarf wizard wasn't creating a new class. A Halfling in 0e as a fighter or Thief was different from a B/X and BECMI halfling. 0e has far more in common with AD&D than Basic to me as a result of this and as a simpler alternative to AD&D appeals to me more than B/X and derived systems.
WHat I "get" is that the race as class concept bakes the race and class ideas of 0e into one simple class system instead, re-enforcing the archetype of Elf as Fighter/Wizard multiclass without complicated dual classing rules by requiring large amounts of XP to level up and Halfling, who gets the short end of the stick in B/X, as a soft thief/fighter multiclass... extremely squishy while the poor dwarf is just a dwarf fighter. It's a less than elegant solution to an arguable problem that Swords & Wizardry shows isn't so much of a problem.
So, this is a very brief nutshell of how this all evolved and how I think of it.
You have OD&D, which is the following-
The original three books (LBB), plus the supplements. (Arguably, you have additional material from Dragon Magazine, Strategic Review, etc., but I'm trying to keep it simple).
Then, you had Dr. Holmes streamline and re-publish OD&D as a "Basic" set. That's the first Basic (Holmes Basic). Notably, it does
not contain much information from the supplements. It's the LLBs plus enough information additional information to make it all workable. At the last minute, knowing that AD&D was going to be published, there were references in this Basic to AD&D, but it wasn't made specifically knowing about AD&D.
Then there was AD&D (1e). AD&D is, for all practical purposes, all of 0E (which includes the supplements), plus additional information from Strategic Review and Dragon, plus some additional edits and changes made my Gygax et al. It is the natural inheritor to all of OD&D. AD&D wasn't really that different than OD&D with all the options turned to 11 and some additional rules to make it cohesive. Well ... semi-cohesive.
Finally, there was Moldvay/Cook B/X (which later begat BECMI, which begat the RC etc.). This edition ignored AD&D and went back to Holmes and 0E again. However, it did introduce a few changes- notably, the race-as-class- to keep the rules streamlined and simple.
Whether race-as-class is stupid, or a reasonably elegant and simple solution for making archetypes, is in the mind of the beholder I guess. At the time I thought it was stupid and juvenile. But now, I appreciate the genius of Moldvay. YMMV.