For those who have no understanding of 3D Modeling, what the dev did here

What exactly makes it so "unmoddable"?
Well, it's not a texture, but individually colored vertices, each strip is it's own material set you need to manually change each attribute manually. What the fuck did I just say?
Without going too technical, well, imagine you have a plain wall, & you want a design on it, & you can easily just put a wallpaper (texture) & be done with it. However, instead of doing that, you draw that design by hand, which is a waste of time (loading time), resources (processing time), & even space (just think of the paint boxes or something as storage space. Shit, this really is a guide for dummies, made by a retard).
This shit, is the equivalent of Yandere Dev levels of bloat. I won't go too technical, but here's the list of issues:
The Topology:
The dev is a fucking troon, doesn't even get out of it's house. It can't even achieve to learn immaculate topology.
NGons:
Those black dots you see on that flag, there should never be these many, even his own followers are shitting on him for this.

It looks like a purple asshole kek:

There's a lot of edge loops that serve no purpose, but take away more processing power, thus making the game noticably slower when you have a game filled with shit like this.
The Poly Count:

This is what's mainly causing the bloat, even if you are a nigger, faggot, troon, or worse, a troonniggerfaggot, who likes this shit. That polycount alone is worth removing this shit.
Vertices - You could remove at least half of the vertices & still keep the basic shape of things. This is said purely from an optimization standpoint, however, I think the extra vertices are for animation without cloth simulation the only thing with really messy ngons is the circle. Yet, there's the issue that they're not uniformly spaced out so it's not to have cloth physics.
I'll be honest for fairness sake, it's not that big of a deal, something like 170 won't rape the game's performance by any means, but it's still unnecessary bloat.
Triangles - Basically, a flag doesn't need that many Tris. For example, A sandwich in Starfield has 90,000 tris. But if you know how to do it right, you could make a fully rigged (movable model) being under 5-6k tris. To put into perspective, there's around 100+ unnecessary Tris in that flag.