[Marsh.]

I don't think it's so much to do with them getting the casting wrong. On paper BB10 was awesome with a great cast but in reality the series was very boring without the twists.

I think maybe it's not that they're choosing the wrong housemates but there's nothing new to see anymore. We've seen all the variations and mixture of personalities we could see so it's no longer refreshing.

BB4 saw "normal" people getting boring and no longer interesting, then BB8-11 saw the more boisterous and freaky people get old.