It certainly is inevitable, for all the reason you say, and I think it's about time everyone in the music industry admitted it, that there is no such thing any more as truly 'original' music, that everything sounds influenced nowadays.
I mean, what about all the new indie bands? The Enemy = The Jam
Editors= Joy Division. Kaiser Chiefs= Madness. Arcade Fire= Talking Heads. So it does annoy me somewhat when Mika is criticised by some as being 'derivative' - because everyone else is, too!
I've been listening to music for 4 decades now (:wheelchair: ) and I can pretty much reference everything new I hear back to something else, so it's really no big deal if Mika sounds like 80s female singers is it he's no worse than anyone else! The trick is to put your own twist on things, which Mika does perfectly.