No, you don't. (And for broadcast's sake, they better not need them because they're not getting them, and haven't been for a while now.) Even American Idol only gets 16M nowadays, which is 5% of the total population.You need the general public on a network
That means (except for sports) every show on broadcast is a niche show. The only question remaining is, how big is the niche and can it pay the bills?
Once Upon a Time is showing the way. That's definitely a niche taste - a serialized drama about the tribulations of fairy tale characters? With 9M viewers, it appeals to only 3% of the population, yet is one of the big new hits of the season.
Any of the new sf/f premises could theoretically also appeal to 3% of the population. That's getting pretty specific. I think the best strategy is to untether completely from past ways of doing things. Don't do what Alcatraz did, and try to pass off a cop show as sf/f. You just annoy the people who want sf/f, who are the only audience for the show.
Instead, just fling yourself way out there like OUAT did, and see if there's even a little niche for you to appeal to, because that's all you need. Give them exactly what they want, and they will be loyal. It's a small target, and you have to hit it dead-on. That's how shows will survive going forward.
From that perspective, I'm less sanguine about the mystery-based premises like Revolution and Midnight Sun, and more positive about Beautiful People, which tells the audience what it's really all about, up front: it's a civil rights metaphor using androids. If you like it watch, if you don't, don't. But nobody needs to worry about being strung along waiting to figure out whether they like the damn thing. I think people are getting really sick of the Alcatraz experience (and shows like that are probably contributing to the low ratings that broadcast gets overall.)
And they're lucky they're on Friday because on any other night, it might be cancelled (since it's also on desperate NBC, I can't say it would be for sure). But it's funny that even trying to use an audience-pleasing trope like the cop show format, Grimm is getting substantially less of an audience - 5M - than OAUT, which is flying without a net. The lesson there is that being chickenhearted isn't going to pay off for broadcast like it used to, not unless you're CBS.there's a reason Grimm is a police procedural wrapped in fairy tales.