The "I've never heard of them" argument doesn't really matter, part of the show is getting to know the people and following their journeys and seeing how well they can pick up and adapt to dancing. I bet a lot of people had never heard of Joe Sugg from last year (I certainly hadn't) and yet he was a massive hit with viewers. I would say many will do the same with a lot of this years contestants.
Yes, true, but you still need to draw people in with at least one or two familiar (to them) names.
I'm not so sure that's so relevant these days - the show is almost bigger than the celebs. You know you're going to be entertained whoever the celebrities are, and will enjoy their development. The key thing these days is trusting that the producers will make a show we want to watch, and have chosen celebrity dancers who will entertain us, whether we know them or not.
I'm not sure I've ever watched Strictly because "Celebrity A" or "Celebrity B" was on it - and I suspect I'm not alone.
The celebrity booking over the past few years has been pretty effective - covering a nice wide range - sporting stars, TV presenters, soap actors, social media personalities, radio presenters etc. This year they don't have someone from a pop music background - but apart from that most bases are covered.
Lou Scannon and Jay Lee gave kudos