Weren't you guys just arguing the opposite of this viewpoint with regard to Martial Practices? I could swear (without going back to check, I admit) that AbdulAlhazred said something along the lines of "as soon as you have an MP for Create Fortified Campsite, now you no longer can create a defensible location via ordinary means without the MP."
Please don't get me wrong: I very much see and agree with your overall point regarding turning everything into an (optimized) Arcana check. I'm just trying to conceive of ways to make ritual use more of a possibility in my own game, one that doesn't compete with combat resources (as I've discussed them above).
Well, that is an issue. However I distinguish between some sort of general knowledge and some highly specialized knowledge. I mean, nobody thinks that every character in the world knows how to create a magic ward, or summon a demon, or build a highly complex trap. Most anyone can attempt to make a passable deadfall though, given time, resources, and motivation (I mean most people in the real world could at least attempt this).
The point is, a 'skill' Trap Builder, that covers all possible forms of traps including simple deadfalls, creates enforced incompetency. It means characters are constrained from trying ordinary things, or else if they buy the 'skill' they're being shortchanged because people without it can still do the same thing. Now, you could carefully price the 'skill' to account for this, or you could carefully word it to only be applicable to say 'Highly complex mechanical traps'. Or you could simply make it so that it gives you a vastly higher chance of success, even with simple traps (like maybe no check at all). In fact making it simply a narrative device, as I've suggested with a lot of these 'skills' (using the term loosely here) accomplishes that. Having 'skills' allow substitution of one type of check for another can also work, so 'Arcane Wonderworker' that provides substitution of Arcana for say Thievery to set up a trap would seem to be worthwhile.
So, for this example, I might consider there to be a 'practice' Trapsmith that lets you set up ordinary traps with no check needed at all, you can just make a deadfall, its a good deadfall. You can also make other more intricate traps, though you probably need special materials, tools, time, and probably a check to see how it came out (as part of an SC). Yes, there's a tiny niche 'enforced incompetence' involved, every Dick, Tom, and Harry can no longer make intricate mechanical traps by default! There's still a ritual, Arcane Trap, that lets you make purely magical traps, which is an alternative, and there's a feat (or something) Arcane Wonderworker that allows substitution of an Arcana check for 'making things' that would normally rely on Thievery, Dungeoneering, etc. (its a bit ambiguous in 4e how exactly traps are made TBH, so I'm not sure of the exact wording here, plus it might apply to other similar mechanisms like clocks or something).
Honestly, I think the whole area of game design is a tricky one. There's not one single perfect way to handle the intersection of skills with other character resources, etc. You probably have to look at things on a case-by-case basis to some extent.