Ancalagon
Dusty Dragon
As has been pointed out old school rule sets are not light.
Debunking the misinformation you are spreading from your description of modern systems as complex when compared to arcane older systems to your leap to it being about trust issues.
Well... which old school system are you looking at? AD&D 1e (which as you say, is a mess), or B/x? Look up the OSE version.
The thing is that happened in 3e was that they did great work in solidifying and unifying the mechanics. BUT once they had that solid foundation, they built up on it. All the simplification gains were lost because of this.