I dont know. I am very satisfied with the bang for buck experience with my core rules books for 4ed, 3ed, traveller, odnd, and hero. 30 years ago I saved my allowance (and a bit of lunch money) for a week and a half to get the 1st ed player's handbook. Today I can get a core rule book online for what amounts to the price of a shirmp poorboy and a bottled water.  Of course you will encounter diminishing returns with add-ons. But just because something is produced doesnt mean you have to get it.

In games, the source of excitement varies from player to player. Some enjoy the visceral appeal of rolling a butt-load of dice. Some like seeing a 20. Some like meeting an NPC tied to their back-story. Each type of player has different motivations. Like with football some folks aren’t going to like playing goalie.

The  coinflip game system I offered  might be dismissed out of hand though it fulfills every one of your requirements. Its flexible, fast resolving, covers any situation you could conceive. The issue is that most players wouldn’t find it very exciting. Its all Fluff and no Crunch.

The thrust is, simple game systems exist but the problem isnt a fundamental one of system rather its of expectation of effort. You are not going to get fit watching TV no matter which program you watch. Eliminating the crunch (rules) to bare minimums means you have a lot more work to do Fluff wise to maintain an rpg experience. Systems with enough latitude to allow any Fluff requires some level of crunch to facilitate the diverse situations in a robust way.

Any game system can fade into the background if you master its working concepts, but the skill in gaming is relating those concepts to characters and situations. Looking for the simplest set of concepts to master (coin flip) helps isolate the “Fluffy” skill set but the variety of player preferences out there necessitate some compromise between the two extremes.  The positioning of (gurps..Gurps lite? Multimedia File Viewing and Clickable Links are available for Registered Members only!!  You need to or ) as too complex to merit consideration seems to be asking to move along both ends of the spectrum at once.