Fred Brooks wrote in 1975:
Show me your flowcharts and conceal your tables, and I shall continue to be mystified. Show me your tables, and I won’t usually need your flowcharts; they’ll be obvious.
It’s easier to understand D&D from reading a really good module than it is understanding it from reading a really good rules text. (Now, having both is way better than just having one.)
I was looking for blorb for many years; I couldn’t figure it out even after reading hundreds of core books and a handful of the typical linear “adventures” of the 90s.
For a while I thought D&D was the missing piece. “Why did I let fans of GURPS / WoD / Everway / Fudge scare me away with their talk of how illogical AC and HP are?” And, yeah, maybe. But reading B4 The Lost City is what helped make me get it, much more than reading the rules booklet.
I’ve complained that games like Lady Blackbird and the original edition (fixed in later editions) of Cthulhu Dark were just “half games”. Even GURPS. The rules for the DM are missing. (3:16 and AW2e do a better job in that regard.)
Whereas Neverland or Hot Springs Island have a much more useful half. You can grab a one page stat block for your character a la Searchers of the Unknown and have a great campaign.
I do run a pretty rules-heavy campaign. I have, and like, both halves. But if forced to give someone only one half, I think they’d be better of with the half that gives rules for the GM. Modules, or location construction kits like the 1e or 5e DMG.
I was frustrated in the 90s with the games that were extremely heavy on the PC side and then just “lol make up some stuff” in the GM side. Half games. I suspect these games were very useful to those who either grew up on D&D themselves, or learned from someone who did, but to me who didn’t know about D&D basics, there was something missing.