Originally, RT was more or less a 'good faith' measurement of the general sentiment\quality of a film, but it is so easily manipulated it was inevitable that it would become meaningless.
While they definitely measure on different metrics, the goal of a critic is supposed to be to measure films worth watching (even if only for a subset of the total audience). When 95% of critics tell you to see a movie that only 10% of people enjoy, something's broken.
It depends on what you mean by "worth watching".
You can't apply necessity to art. I don't have to eat some shitty art-film to survive.
* - Hate is probably an overloaded word anyways. I don't know many kids who genuinely "hate" broccoli, they just think eating broccoli means they won't get ice cream because they don't have rational thought processes and can't think/imagine beyond the next fifteen minutes. Adults can, and so the distaste is less extreme, because they can have ice cream on their cheat day. But obesity rates would show that nothing really changes, in how much they "like" things.
Of course it's impossible for one person's evidence to refute what happens "in general", but either this isn't true for me, or I don't understand what you mean. I love broccoli. I don't hate ice cream, but I certainly wouldn't eat it every day, which I'd be happy to do for broccoli. I don't think I'm responding in any significant way to external factors, only to eating one regularly making me feel better than eating the other regularly. I don't imagine my experience to be universal, but nor do I imagine it to be very rare.
However, I addressed your point:
> obesity rates would show that nothing really changes, in how much they "like" things.
If everyone loved healthy food and hated treats, obesity rates wouldn't be so high, and Frito-Lay wouldn't be one of the most profitable food companies in the world. Obviously, no general claim is universal.