That color scheme was allegedly picked for visibility on very low-end TV sets. (The Amiga palette colors could be chosen arbitrarily from 4-bits per channel RGB, so that wasn't a constraint.)
(The icons weren't just arbitrary sized, they could have different pictures for the selected and unselected state. You see this with the open vs. closed drawer icons (drawers are like "folders" in other OS's) but many app icons also used this effect.)
Be that as it may, if you look at C64 GEOS which ran on consumer TV sets and with comparatively primitive hardware, the UI looks so much nicer in GEOS to my eye. Even the Apple II GEOS makes Workbench look like a hot mess.
There weren't any 'default' icons, so the workbench didn't show you everything on the disk, only programs with ".info" files which had the icon. You had to drop to the command line to do most low level things. Of course, Workbench didn't really matter when you were playing games.
There was an option to show everything - with default icons. (Not very useful ones since notions of document ("project") file types were not used all that much, so every file showed as some sort of executable. But the option was absolutely there even though it wasn't the default.)
Only on WB2.0+, for a decent number of years we didn't have that.
At the time though it didn't seem any worse than the Mac though, and it had colors - even if the defaults weren't great, any colors seemed better than none.
Or at least that was how tasteless teenage me saw it.
https://guidebookgallery.org/screenshots/amigaos10
It seems they had at least 64 colors to choose from and they went with... Orange and white on blue? They also decided icons should be able to be arbitrary sizes for some reason, a feature I haven't seen in other GUIs.
Here's workbench 2.0, which is better but still pretty unappealing.
https://theamigamuseum.com/amiga-kickstart-workbench-os/work...
Scrolling through I thought "wait, that one doesn't look too bad" and then realized I was looking at a screenshot from Windows.