Yeah, except generally speaking, you don't have "guards" be the same level of effort at "Dirk the Dastard" - the guards are likely mooks, and Dirk, being named, is probably a significant challenge. I submit that if the PCs are as likely to beat the guards as they are to beat Dirk, going through the extra effort for Dirk would be a bit anticlimactic, and that probably doesn't fit the narrative needs (unless you are using themes of villains who are kinda pathetic, when all is said and done).
The extra detail is interesting when the different detailed choices matter to the result. It is busywork when they don't matter.
Don't believe me? For your next gaming session, set up a complicated decision process - make it take a half hour - for choosing dinner for the group. But, all end possibilities for the process are "pepperoni pizza". Make them go through the exercise, and then tell them that no matter what they did, the end result was the same. Ask if they feel the process was valuable, given the inevitable result.
Yes, you may get some people who like the process, but I'll still expect they'd say, "We could have just gotten the pizza, and then done the process in a way that it actually mattered, and I'd like that more."
Couple points: 1) The guards are not necessarily the same effort, individually, as Dirk, but they could be the same effort in a group, or, even if they were less effort--they should be
some effort, so need to provide some level of expenditure of resources--which is why you can't just handwave. There's also a matter of time...I may need a quick game, so I use the "quick" way of resolving issues, and the "complex" way when we have the time to indulge in more details. So the quick and the detailed need to create similar results. The complexity should be there when we want it, and not there when we don't. It's like having "Basic" & "Advanced".
Combat is not the only area where this comes up; one needs some kind of quick resolution method for abstracting the search of every chamber in a dungeon, but when the situation warrants it, there needs to be a way to engage the fiction in a more granular fashion; just like in movies where long stretches of time can go by in moments, and then short moments be given great detail.
As to wasted effort, that's really in the eye of the beholder. RPG's are a pastime--any effort expended is, one sense or another, "wasted". So it depends on what one enjoys. I think, like a lot of rpg fans, I enjoy complexity...in moderation, and like to be able to choose the level of abstraction I want in a particular situation.
In the example about the pizza, sometimes I need one fast, and order out or cook up a frozen pizza; other times, I enjoy preparing my own dough, prepping it, slicing up the ingredients, preparing and cooking myself. At the end, in each case, I have "pepperoni pizza", but the amount of effort I have invested greatly differs, based on my desires at the time.