Even senior professional candidates can be quite vague about how things like this work, which is understandable in some ways because well, this stuff just works, I'd investigate if I needed to. OTOH intern candidates can be very clear-eyed and curious about all of it, and can figure it out on the fly.

At the very least you should be able to take 0-1 uv coordinates, translate that to a lookup in a linear texture (knowing its dimensions), then think about linear interpolation to smooth it. But then why is this still so speckly?

Graduates with fresh understanding of information theory/sampling might know where to go next. Not straight to mipmaps perhaps, but figure something out without them, like averaging over a larger area of the texture. Can you precalculate that larger area? Oh, that's mipmaps. How might the shader know what two mipmaps to select?

Coming from another direction an EE graduate might have some of that but also see things about latency and bandwidth more clearly, and realize tiling/swizzling could be useful vs. storing textures linearly.