The problem with not having a rule-based solution is that the GM and/or players have to put effort into making sure it works. The problem with a rule-based solution is that rules are inflexible - so that either things some players want are prohibited, or the GM and players have to put effort into making sure things work, regardless.
It comes down to a simple fact - no finite and usable ruleset can do *everything*.
I'm not sure I agree with the bit I've bolded. A ruleset like Fate or Heroquest, rules light, with a clear resolution mechanic, may take work from the GM and players, but it is not hard to find a resolution that is rule-based. Both games are almost written to make that possible. Neither would necessarily satisfy someone who wants the degree of detail found in D&D (at least in it's combat resolution), of course.