It was, up to a point. Towards the end of the war, you see the same sort of desperate insanity and careless waste of resources that gripped Nazi Germany when they were losing the war. The Nazis wasted unspeakable levels of capital on wunderwaffe that would change the tide of war, but didn't have a snowball's chance in hell of being fielded, or even working. Big artillery cannons, inaccurate ballistic missiles, next-generation U-boats, even bigger artillery cannons that have to be built into a hill, you get the idea.

So, with the UNSC, you have NOVA bombs that they had no practical way to deliver, but instead are forced to target massive Covenant fleets that cluster up to make your job easier. You have a new class of child suicide troops being trained when augments fit for adults are on the drawing board, and you have another supersoldier program where the objective is to make augment them to the point where they don't need armor. Maybe they have bulletproof, plasma-resistant skin?

And then the UNSC Infinity took up half of the Navy's budget before the UNSC had the technology to make it not die spectacularly in the first engagement against a Covenant fleet.

So, yeah. Impractical, fanciful, but the UNSC needed something that would change the tide of the war. Something revolutionary, like how the conical bullet and the railroad changed war in the 19th century. But we've gone beyond that. This post-war armor, where each Spartan seems to be getting an individualized armor type and we have armor that's literally inspired by ancient Spartan helmets or samurai, and there's at least three different sets for tracking people, is some weird COBRA shit.