Vanilla GNOME3 looks and feels a lot like it was designed for tablets as the primary target, keyboard users as the secondary and mouse users only as the third.

Ubuntu Unity did not - it was great for classic desktop usage with Mac-like (most importantly, not a mediocre attempt to mimic but even better than the original in some aspects) UX + advanced supports for keyboard lovers + keeping the mobile in mind.

IMHO late years Unity was the best Linux UI yet. If only they would add Pop_OS!-like tiling + some more little Mac goodies only experienced Mac users know it would be perfect. And I absolutely can not say the same about GNOME3 although I actually want a GNOME3 tablet.

It was designed for touchscreens and desktops; a so called convergent interface. For example HUD, which allowed you to search any menu option (ref: https://wiki.ubuntu.com/Unity/HUD#Overview), and its Dash, a desktop search utility, were clearly keyboard-oriented. The bigger icons that launcher and dash had were probably made that way for touchscreens.

Unity was originally designed for netbooks with limited screen real estate.