On the contrary - "Plasma" is one the best branding efforts in the open source ecosystem so far.

It's not really confusing or hard to search for if you know that "Plasma" is a KDE product - for instance, Plasma Bigscreen is the first Google result for "kde plasma tv" and "kde tv". It's 8 years old, it covers several different products with a similar look and feel, and it sounds as cool as it looks.

Big brands don't have an issue with using common words for product lines (like "surface" and "pixel"), and I don't see why open source should cede that ground.

I agree with what you’re saying, but you could’ve said it nicer.