That might be a little bit controversial. In any case, I'll controvert it.
FWIW, whether or not it is a design goal, 5E does pretty well in this niche, partly because "balanced" is so oddly defined. (150,000 XP of Tarrasque is orders of magnitude easier than 150,000 XP of hobgoblins or drow!) Asymmetrical skirmishing is rarer than unbalanced encounters but still well-supported due to Stealth rules and movement rules which let an inferior but high-quality force take on and gradually degrade a more powerful force (PCs = Special Ops). The main thing 5E is missing for this scenario is abstract rules for defeating an enemy in detail, which means that it's kind of up to the DM to either eyeball it ("there are only 20 hobgoblins in and around the command tent, but if an alarm is sounded, 2d10 more will arrive each round until all 300 are present") or to make up his own rules. But that is more an omission than a conflict: 5E still does asymmetrical skirmishes quite well.
Of course that doesn't mean that all 5E characters will do equally well as asymmetrical skirmishers. Rangers for example are fantastic in that role; paladins not so much. (No AoE, melee-oriented, trouble with stealth = problematic.)