I'm just following the OP's lead.
I think the point about classes is an important one. Maybe the knife-thrower should be a rogue?
But this also creates tensions with Oofta's point. If it's true that a thrown knife does a lot less damage than an arrow from a longbow, then why - when a rogue uses a thrown knife - does it do so much more damage than a fighter's longbow?
This is one of many reasons why I think discussion of viable archetypes isn't something that is helped by considerations of "realism".
But this isn't a reason why (eg) warlocks should be better ranged-damage dealers than featless fighters, is it?
In 4e, Cloud of Daggers is a wizard spell. Maybe you're thinking of Blinding Barrage? I'm not sure why it's particularly impossible (anymore than the other action heroic stuff that happens in D&D).
If you want a knife-throwing character, it probably should be a rogue. You can always use a bonus action to throw that second dagger if you miss with the first. It may not even be a bad build if you have a way to get opportunity or other attacks outside of your normal turn on a regular basis.
However, the long-bow wielding rogue will do more damage on their turn than the knife thrower because long bows do more damage. In a more realistic game, a long bow should do significantly more damage, but that's one of the (many) compromises D&D makes.
As far as 4E, Blinding Barrage (thanks for the correction) was one of those powers that always struck our group as something simply impossible to do outside of an anime cartoon or superhero comic genre. I'm not saying it's good or bad, but PCs in 4E that were supposedly not using supernatural powers did things all the time that would look out of place in an action movie. Non-supernatural PCs in 5E (and basically all non-4E versions of D&D) push what is possible, but at least what they do is a close facsimile. I don't have a problem with wizards casting spells or barbarians getting a boost from their totem because those things are explicitly supernatural.
I don't want to get into a 4E vs 5E discussion, just saying that the only way I see you getting a dagger-based build would be some niche that had supernatural abilities of some sort that could only be done with daggers.