That isn't wrong, but that has less to do with the idea of the subraces themselves and more so with the stat restrictions imposed upon them.
The Juggernaut (which is a just your stock dumb bruiser type) is an obvious design for a weapon of war in a world where guns don't exist. Unfortunately, in 5e, STR underperforms, unarmed strikes don't really work unless you are a Monk (and monks don't use STR), and Powerful Build is already on like 5 other races (making it a kind of boring power). In the end they have one good unique combat ability despite being "designed for combat." They could have thrown on some kind of extra weapon damage to help make up the difference.
The Skirmisher, on the other hand, totally outperforms the others in weapon based combat by virtue of having more movement speed and using Dex (which overperforms unless you are using a two-handed melee weapon, and even then it isn't a bad 3rd stat for a Ranger or Barbarian). The third ability of being able to move at normal speed while maintaining stealth for overland travel makes them ideal for weapons. For starters, they should have been small, but even then they would still be relativly high on the totem pole.
Finally, the Envoy just isn't well built for war at all. It does have floating stats, which is more useful for a greater range of classes and subclasses. But other than that, they are all about tool use. Which makes for fun and interesting concept characters, doesn't make for killing machines.