Among language computing professionals, these square boxes are commonly known as tofu – yes, those yummy squares of bean curd common in East Asian and South East Asian cuisine!
It may not have been intended to be derogatory but that doesn't mean it hasn't ended up actually being derogatory. "No more tofu" certainly sounds like a judgement that "tofu" is bad/unwanted
Homonyms are a thing. Of course a thing can also be good in one context and bad in another. No more tofu spilled in the bed. No more tofu spilled across my blog. "No more tofu" out of context sounds like a soy allergy. With context it means exactly what it says; eliminating a UX failure mode.
If something can only be derogatory if you fundamentally change the actual meaning of the statement, I think it is proven the statement as-is is not in fact derogatory. I would go so far as to say, it's abusing the notion and nature of human language to claim otherwise.
