Side note: I’m kind of shocked that they dropped the isomorphic style for the icons. That was a truly... iconic! aspect of the BeOS visual language. And quite modern in my opinion!
The pixel-perfectness of the UI was also iconic. If it were me, I’d go back to isomorphic and go deep on a rigorous system-wide grid. You can still do vector icons but be meticulous about the grid.
I think you mean isometric (that's where the X, Y, and Z axes all have the same scale, and are 120 degrees apart).
Fun fact: pixel art is usually not-quite isometric because they use a vertical line and then lines that have a slope of 2:1 which is about 7 degrees larger distance between the X and Y axis[1].
The pixel-perfectness of the UI was also iconic. If it were me, I’d go back to isomorphic and go deep on a rigorous system-wide grid. You can still do vector icons but be meticulous about the grid.