Buying a coin solely on the basis of it having an ID'd developer is just as foolish as buying a coin because it has a pretty logo. A developer who refuses to identify himself, however, is a red flag. If a coin accumulates enough red flags it's best to avoid investing in it. Crypto is like poker. The key to winning isn't usually winning more. The key to winning is to contain your losses.
I don't think it's a red flag at all. Most people in the crypto community wish to remain anon and if I was a dev I would definitly want to remain so. Those guys get a lot of heat and let's not forget the guy that started all this is still anonymous and nobody has any idea who he is and I'm glad it's that way.