If your argument is that anyone who isn't on the level of the hero is worthless, then heroic stories will always disappoint you.
If Arya Stark can just swoop in and murder the Night King, why did we need all the other troops? They're all worthless, right.
If Legolas can just jump on an olifant and snipe it down, what's the point of the entire army doing shit? WORTHLESS.
And so on.
That's not how it works. We don't even know how good those elven troops actually are. We know that getting ambushed by a snow troll after being half dead from exhaustion and exposure did not lend itself to them displaying overwhelming force. The hero who has been shown even before this to ignore all those things and march on driven by single-minded determination does display such force. And, mind you, does so in a way that IMMEDIATELY and WITHOUT PRIOR COORDINATION makes use of her troops in support (though in a very goofy way), which suggests that they ARE skilled and ARE accustomed to fighting, they're just running on fumes here and can't do much more than lend a hand.
This shows nothing of how good the troops really are, because we have no basis for comparison. All we have is them vs. Galadriel, where she clearly comes out on top. As you would expect a hero to do, and as heroes are consistently treated in heroic narratives where they are stronger and more skilled than random soldiers, less affected by adverse conditions, and more determined and driven. All of which is demonstrated here in exactly that very standard, very tropey way.
But that's development. You see how it was before - then you see how it is now. Showing her abandoning her support (or being abandoned by it, however you want to frame it) is very different from showing her not having any in the first place. Those are not the same thing, narratively, just because they look the same at the end. That's like saying why did you show a character getting divorced and then moving into a motel, could you not just have shown them living in a motel right away - them losing something they had MATTERS.