The way I look at it, the old school D&D (and by extension games like LotFP that are based on it) gave you a basic framework for how to handle all the really common actions; things you'll be doing on the regular. Anything else you came up with, you just made it up as you went along with spot rulings and hand waving.
Newer games (like Pathfinder and modern D&D) kept all the basic framework, and then also tried to codify and balance ALL the different spot rulings and hand wavings; they tried to make the rules cover every possible situation. That's why you need 5 kilograms of book to play Pathfinder.
The problem I have with the new game approach is, it creates a mentality of rules informing playstyle. When you want to do something, you look up the rule for how to do it, and then follow that rule; if there's no rule that tells you how to do it, you can't do it. Old school D&D stays out of your way much more often.
Over the last few years, I've been migrating away from all the games with fiddly bits, heh. I still play and enjoy Pathfinder and Warhammer RPG (Rogue Trader/Deathwatch/etc) and Shadowrun and all them, but they are never my first choice anymore. I tend to go for the rules-lite systems, like LotFP, Savage Worlds, Dresden Files (Fate system), and the like.