It's a "weakest link" thing: all it takes is one fuckup and all other components of your security become irrelevant.
You are correct. It does take one fuckup.
But what if (hypothetically) you bought the printer and turns out printer has a sim in it that sends every single print job via cellular n/w to server.
You trusted the printer but printer itself is at fault whose fault it is?
Are you seriously comparing using well-known compromised malware for key generation to something that's generally considered as being completely impossible?
You are correct it is impossible. Just creating a hypothetical scenario. who will be at fault?
Of course it is impossible but if it does happen Or say someone randomly writes a key and it happens to be your wallet. Who is at fault?
Let's consider another example, we know many other creators in forums use bitaddress.org, if tomorrow turns out there was some vulnerability with that site,
and all keys are compromised, who is it at fault?