I do not see how it is relevant if sources use the word famous.  We are never obliged to use the same words as any source.  You can find a source claiming that almost anything is famous - it's hardly a rare case where lots of sources do so - so should we describe everything as famous?  No, I tried that and it was rightly shot down.  You can find a source - a famous one! - which says that this opera is a shabby little shocker.  And those words aren't even listed as ones to avoid, so do we use them as if they are objectively true?  Obviously not.
I don't believe the word is forbidden on Wikipedia, I already said that.  But we have a guideline called "words to avoid".  It doesn't say "avoid these words, unless you really want to use them", it doesn't say "avoid these words unless you see them in external sources", it says "avoid these words, because they neither impart nor summarise verifiable information".  The guideline is very long established, and I see no sensible case for an exception here.  200.83.101.199