Corner kicks aren't the stuck on goalscoring opportunity that some fans see them as anyway, they're merely a means of restarting play albeit you're getting a free cross. But it comes at a cost... of course the opposition have time to organise so it's not like a cross in open play where you're breaking quickly.
I read a statistic a while back that showed corners vs goals converted and free kicks vs goals converted... not many goals are scored form corners at all.
And yes, City do comparatively well from corner kicks compared to the rest of the PL teams. But we're a "glass half empty" group of fans, always have been.