I happen to love the show, but maybe that's because I don't take issue with cliche's anymore. Part of my transformation on how I feel about the subject of cliche came to me as an epiphany: something isn't cliche if the audience doesn't know its cliche. I know on the surface that just sounds like pointing out the obvious. But it's a bit more complicated than that and goes back to my feelings on writing in that you (as a writer) need to know who you are writing for. You need to really identify your audience.
For example, if you are wanting to be a mainstream fantasy writer then you probably should know that dragons are cliche monsters and that fanciful and strange magic systems that no one has ever heard of are important. Why? Because your audience is made up of people who have consumed every Brandon Sanderson, George R.R. Martin, Brent Weeks, and etc. book that's out there (ravenously). Just like in academia, there are geek experts (think "Geek PhD") that have been there/done that on just about every kind of fantasy and are just ready to say the following to your idea: predictable, boring, cliche, saw that coming a mile away, plot's been done a million times, and this is just a rehash of blah blah blah. That's a tough audience to entertain.
Anyway, my point is that "Legends of Tomorrow","Arrow","the Flash", and even "Supergirl" are not shows that are meant to appeal to the PhD's of Geekdom. Sure, some of the audience is inevitably captured, but I think the CW is using sex appeal (because all of its young actors are gorgeous) to rightfully draw in a different audience that hasn't ever heard of these characters. And because of that, these shows are doing really well. In other words, men and women are drawn to these shows because they see some eye candy and are staying because the cliche's grab them. Now I know that sounds weird, but think about what a cliche is. A cliche is something that is basically a good idea and because of that, everybody else got in on it and pounded it into the ground. It's the bread and butter of America. Oh you came up with a phone that allows you to install apps that do other things? Well that's a great idea and I'm going to steal it. Another example: wineries. They started making money a few decades ago and bam...there were suddenly thousands of wineries and because the competition was so vast, no one made any money and wineries started going bankrupt.
So when I see what's going on with the CW, and how I think they are capturing the attention of a whole new audience by hooking them with sex appeal and making them stay with cliche ideas that actually aren't cliche because this audience has never heard of them...it seems kind of brilliant. And I think it's something that all new writers should thing about. Create a hook with your writing. Draw a fresh audience into a genre you enjoy that's packed with experts just waiting to call you on every cliche you could ever come up with, and ignore the experts to cater to the new audience. In my own writing, I've been very satisfied with the results. Basically I've been writing gay fiction, and suddenly I'm finding that I don't have to work very hard on my science fiction and fantasy ideas because to the particular audience I've been writing all the ideas are relatively new. As an example, I've been able to write a fantasy that's pretty much character driven without giving a second thought to magic systems, and I've been getting fan mail about it. I want to use a dragon? The audience I write for says, "OMG I've never seen that," and it's really kind of cool.
Anyway, I just thought I'd share that with all of you because I've thought about it quite a bit this weekend. A cliche is ONLY a cliche if you know it's a cliche. So for me, my ideal audience is to write science fiction and fantasy for people who normally don't read science fiction or fantasy and then discover that they like it. I know that sounds hard, but I think what's harder (for most of us) is writing for an audience that has expert level knowledge of a genre and is hungry for something new. In other words, I'm saying it's harder for most of us to reinvent the wheel. So rather than try, let's use the same wheel (which we all know works) and trudge down a different path.
In conclusion, I'm saying it's not the cliche ideas that are necessarily bad. It's that you would dare to use them in front of an audience that knows better that's bad. Identify your audience first. If you truly want to try and impress an audience of experts with something that even they haven't seen...well that's on you and good luck.
That is all. :)