This is not a binary thing. There is such a thing as an interface that is clean and uncluttered, while still using icons that are at least distinguishable from each other. Otherwise you get none of the benefits of an uncluttered interface -- e.g. you have to hover by each button and read the tooltip to find the right one, which is precisely the kind of thing a clean interface is meant to avoid in the first place.

Also, Blender is not a grocery list app. While disregarding novice users does result in an application that's impossible to learn and that's obviously bad, it's equally unproductive to optimize an interface for people who see it for the first time. Blender is the kind of application that you spend tens, if not hundreds of hours learning before using it productively (let alone professionally). That's the target audience you're designing for, not people who download it and uninstall it if they get bored in the first thirty seconds.

Sure, my comment is in response to the claim that monochrome icons are user-hostile and pushed by a cargo-culting UX profession.

Plenty of professional tools (Photoshop, Final Cut, Figma) have monochrome icons without it being a usability issue. These are all content creation tools, including Blender. The UI and content should not be fighting for attention. It's clear which of those two should primarily be on display.

I think it's entirely possible that Blender just has poor icons - but it seems demonstrably false that monochrome icons are inherently inaccessible.

My best guess is that Blenders real issue is a lack of structure and clear grouping. Providing the icons are in a logical place, it's easy enough to find the correct one, without them needing to be visually distinct on literally every dimension. But if there's no logic to the placement and the icon you're looking for could be one of thirty, then I agree that's an usability issue - just not that the icons are at fault.