Yes! I'm a student studying RPG design, so I like to think I have at least a vague idea of what I'm talking about.
Some various sources, some paid and some free:
Roleplaying Theory, Hardcore, a series of old blog posts by Vincent Baker. A lot of this stuff is boiled-down versions of what the Forge--which others have mentioned--was all about.
Second Person by Herrigan and Wardrip-Fruin; it's a bunch of essays about roleplaying and roleplaying games. It covers both digital and tabletop, so it's a little all over the place, but it is quite good.
Playing at the World by Jon Peterson. It's a huge history of roleplaying games and related games, which covers less hard theory than it does the evolution of the game itself. Super helpful if you're into the history, less so if you're not.
#rpgtheory on Twitter. There's definitely some flak in there, but it's also definitely worth checking on every week or two, to see if there's been any good threads popping up.
The Arts of LARP, by David Simkins. This is LARP-focused, but it has a lot of good stuff on roleplaying in general, especially the more philosophical angles.
ars ludi, Ben Robbins' blog. He writes about all sorts of stuff, but if you go through the archives and find the green-triangle'd and starred posts, those are the sort of 'greatest hits.'
Role-Playing Game Studies, by Zagal and Deterding. This is another collection of essays (which includes some stuff by Simkins and Peterson, too, IIRC) and is kind of the go-to for this sort of thing.
And the Forge, as mentioned by others.
That's a pretty good list of theory and texts and stuff.
One of the ways to learn good RPG theory, I've found, though, is to just read good RPGs.
It's also highly worth digging through acknowledgements and credits of your favorite RPGs and then tracking down the names mentioned. If you're reading a big, hefty RPG, like D&D, pay special attention to any consultants, specialists, or other people listed under strange credit areas.
Anyway, when you eventually dig your way through all of this, I'll probably have read some more, so hit me up if you want more suggestions. Those top seven or eight things are probably the best place to start.
Edit: my personal list of games was rather reductive, as several commentators have called me out on, so I've removed it. Go read lots of RPGs.
It may be beyond the scope of your argument, which seems to be "What Alignment Has Come to Mean," but I think every DM would be well-served by considering the origins of the Alignment concept. Playing At The World goes into great detail, but a TL;DR is
Alignment is a carry-over from the Chainmail wargame rules, where it acted as a shorthand for "Which army are you fielding?" It had less to do with ethos, and was more about which units were available to you to select when building an army.
In the Chainmail rules, the factions were limited to Law, Chaos, and Neutrality. Good was synonymous with Law, and Evil with Chaos. It's not until early 1976 in an issue of The Strategic Review that Gygax suggests that the Good/Evil axis is a sliding scale that colors the character of forces aligned to each faction.
The idea of the forces of Law and Chaos were borrowed from the fantasy fiction of the day, particularly Three Hearts and Three Lions by Poul Anderson and the Eternal Champion series by Michael Moorcock.
When you take these three points together you come to the conclusion that Alignment is a feature of the default, assumed setting of OD&D. It's not necessarily appropriate for all fantasy settings. If the driving conflict for the setting of your home campaign is not the eternal struggle between Order and Disorder, and faction membership to Law or Chaos doesn't dictate your characters actions, then Alignment as a concept has little utility in your game.
In my personal campaign, Alignment is not applicable to creatures native to the Prime Material plane (or its equivalent); It only applies to creatures from the far planes (demons, devils, devas, angels) and creatures powered by their connection to those planes (undead). In my game's cosmology, the father you get from Prime, the closer to two-dimensional your fundamental nature becomes. As such, you become vulnerable to magic that acts against that fundamental nature, like Protection from Good/Evil. Such spells have no effect on creatures of the Prime, no matter how Evil or Chaotic they act.