Lines are not perfect in Illustrator

My guess is that you're referring to the jagged lines in the slightly angled lines.

This is normal. The effect is called anti-aliasing, to give any angled line or irregular shape a less coarse preview on your pixelated screen. Don't worry, this doesn't happen in print, or when you scale or zoom in on your artwork ! It's just the very momentarily view on your screen.

Enlarged:

This is what a screen would render if it wouldn't be using anti-aliasing:

And the enlarged view:

Although the pixels have been very strict in either black or white (which might seem sharper), the on-screen rendition just feels too sharp ! So that's why it's a good thing to soften the edges a bit, and let the software calculate how pixels should represent values in between.

I'm not sure what imperfections we're supposed to be looking at.