Spending five minutes doing something incredibly boring is only "better" than spending half an hour doing something incredibly boring if you aren't repeating that five minutes on the regular.
But then in old school playstyles, every fight with three goblins in a corridor is that. Combat becomes a dull chore, not an exciting event.
Well, at least for 4e, the idea was you don't do the "three goblins in a corridor" things as fights. Fights that are meant to be over in a couple minutes are simply too small; there's nothing to sink your teeth into, no set-piece, just another tiny bit of whittled away resources, and then another tiny bit, and then another tiny bit, over and over. Instead, one way to do them that is faster per fight is to collect many of them together as a Skill Challenge, where one of the possible results of failure is needing to get into a nasty brawl with a larger, more dangerous number of foes, especially because this allows grades of success, e.g. each successful step in the SC reduces the enemy forces, meaning narrow failure vs narrow success is a small gap, not a huge one. This means the Skill Challenge is still more involved than what any one or even three of those combats would be, but you're resolving half a dozen of them sequentially in that time, so there is still comparative time savings.
Now, I have learned with time that this solution is simply inadequate and unacceptable for fans of old school play. That's why I have been working (very, very slowly...) on my concept of "Skirmish" rules. Skirmishes are, more or less, "little" combats. You may know that 5th edition has rules for "group skill checks"--they aren't full Skill Challenges like 4e would've done, but they're clearly more than just a single check too. That's more or less the space I'm aiming for, just applied to combats rather than skill checks. A "Skirmish" should be resolved in at most two rounds, because the whole point is to make them fast, snappy, a way to give teeth to the "whittling away resources" element of old-school playstyles that has kind of fallen by the wayside even in 5e.
In my hypothetical "6e that more or less rebuilds 4e by taking lessons from 5e and OSR games", Skirmishes would be the bread-and-butter of a game run primarily focused on OSR play with only rare usage of "proper" combats, and generally uncommon or even quite rare in a more 4e-style game. Other editions' styles would probably involve a mix of both. You could spend a resource (a limited-uses ability, a consumable item, an NPC ally, etc.) to improve your Skirmish Roll, and there might be rare incidental benefits that make you better at Skirmishes (I imagine Fighters being particularly good at them, for example), but by and large they're a one- or two-roll per player affair, and then you move on.
Again, the whole idea with my hypothetical 6e is that it develops actual, functional, good rules that are directly helpful for implementing multiple different playstyles, but which can still be integrated together if the table desires that experience. It's not quite the "modularity" that the "D&D Next" playtest promised, but it's a damn sight closer than the 5e we actually got. Think of it less like rule "modules" and more like rule...."branches." All of the branches are part of the tree. All of them get proportionate resources and attention. None of them are neglected or ghettoized or dismissed as second-rate. In theory, a single campaign could try to use all of them, but it probably would be unwieldy to attempt this without great care.
