I think I, and a lot of people, respond to ninja, etc., negatively not because They're Silly Words And This Is Serious Business, but just because they're tired and non-descriptive. I have about the same response to something like, "Senior Solutions Manager". It's not a logical reaction based on evaluating the company, more like just an automatic, "Ugh..."
Unfortunately words like that have become a bit "buzzy" with HR and management (non-techie) types: "Oh, so all we have to do is say 'ninja' or 'rockstar' and we're instantly cool and really talented people will want to work here. Can I be a rockstar too, pls?"
I've spent the last twenty years becoming a slacker with more expertise than enthusiasm, so I'm with you there ;)