I think that may make the game boring.
That's one of the criticism of 4E, that a part of the richness of the game world has been lost. 3.5E allowed you to create real dragonslayers and real vampire slayers. (On the other hand, the picture is not all roses. For example: Rogues are useless against undead. As well, a lot of the options for specialists seemed to be poorly implemented, and often went unused. YMMV)
Well, the set-up wasn't to "fix" 4e, it was to have a non-combat role system for 4e. If you're not comfortable with the idea of Rogues being able to sneak-attack undead, you're probably also not comfortable with the level of abstraction that would ask you to be comfortable with your ranger finding their way out of a wizard-tower's teleport maze, but 4e is more than comfortable with that level of abstraction, so it should be OK with this.
That said, ideally, it's sort of a scaling scenario, where you CAN get more complex if you want, but if you don't want, you don't have to. If you want to vary the roles based on environments (wilderness trailblazer vs. dungeon trailblazer), you can add a level of granularity (while yes, having the attached problem that sometimes they will be more useless), just like if you want to vary combat roles based on enemies you face (vampire slayer vs. dragon slayer), you can add a level of granularity (while, again, having the problem that sometimes they will be more useless). Specificity means complexity, so if you want it, why not add it?
I do take issue with the idea that it's
necessary. Clearly, as D&D combat in all editions shows us, you don't need to get that specific to have a good ruleset. If you want to get more specific, there's always other rulesets -- Rolemaster for combat, Traveller for character generation, and more complex noncombat resolution mechanics, too.
If you want to get lighter, you can go freeform.
The rules I sketched out hit a middle ground, adding more detail than 4e currently has, but less than you would apparently want. I think it would be easier to add subdivisions to a role system like that than it would to create a new skill for every circumstance ("Ah, I see you have Swim, but is that ocean, lake, or river?", "Oh, great, you have Craft (stoneworking)! Is that igneus, metamorphic, or sedimentary? Dwarven, gnomish, or drow? Rock gnome or svirfineblin?"), since the over-arching group works the same way. You know any "trailblazer" subdivision is going to earn you successes toward a goal, even if you further narrow it to being only (or most) effective in certain limited circumstances.