Keep watching new things until you find something good. Go after things you'd previously written off as boring or pretentious.
This is a natural and healthy part of your development as a human being. It hurts and it sucks but there's nothing to do about it except beat it back. There are good things out there but you're not going to find them in the same things you liked when you were twenty or however old you were when you liked those things. You know them inside and out and a lot of the newer iterations of those selfsame phenomena are just spinning wheels around thematic ground already trod by their predecessors.
Your options are to either never enjoy anything again or start enjoying things while becoming the person everyone else wants to shut up when it comes time to talk about movies because you can't "just turn off your brain".
Find new things. All the new things. Things that are recently released AND things which are new to you. Try more foreign media (like "different language" foreign) that's not aiming for an international market or that looks really pretentious, try The Wire or similar more actively challenging genres. Stop reading fiction for a while and look at some weird nonfiction topics. If you're a fan of American superhero comics, just stop reading them and try some weird european adventure comics ("Valérian and Laureline" is a good start). Try watching some old Film Noir or silent films, look at weird, underdiscussed films from the 1970s. Heck, maybe even go so far as to start looking into new political theories. Read some bell hooks if you haven't before, check out Susan Faludi or Naomi Klein. Try new kinds of music! If you'd previously written off (as I had in my foolish youth) rap and r&b as genres, try some Kanye West or Janelle Monáe; if you've never been much for metal, at least listen to a single Kreator album. Do you have a favourite essayist or spoken word performer? Find one! Are you interested in historical events? If not, find one to be interested in. If so, find that favourite historical event discussed from another angle and spend a while in the middle of the reading critiquing the new argument.
In fact, just find new things and CARVE THEM APART. Reduce them to their component parts and learn to understand them better than you understand the functioning of your own body.
Your brain is asking for engagement, for challenge, for strangeness, for novelty. You can't stop that thought for the same reason you can't just stop eating. You can't just "turn off" your stomach. Your brain craves new stimulus, new patterns, new perspectives. FEED IT.
You have digested all those other things and taken from them what you need. Eating them again in this state will give you nothing new and you'll just be consuming things from which you've already taken the flavour at the best times and eating stuff you've already digested and expelled at worst.
If you want to get out of things and come to a point where those bits of media can become comfort food that you enjoy in spite of their failings, you need to know that they aren't all there is.
They aren't.
Watch Fritz Lang's "Metropolis", some 40s crime films like "Concrete Jungle" or "Double Indemnity" and compare them to what's out now. Look at the creative DNA that's made up modern films and how little they've changed. Check out Twin Peaks (or anything David Lynch has done) and let the experience wash over you and examine the really obvious THUD in the middle of the second season when Lynch stepped away from the project and it becomes just some TV show for a while.
Read books on the creative process and criticism so that you can hone this new compulsion of yours into something incisive and strong and maybe turn it into something else, like a work of fiction or a research project or a play or a book of poetry. Heck, a book of criticism or a blog nobody but you reads! As MovieBob once pointed out, criticism used to be considered an art and that engagement with that art has fallen sorely to the wayside.
What I'm saying is that this period is painful. But it is survivable.
The people who suffer most during it are the incurious, the ones who hold fast to old orthodoxies or the tastes or politics they developed when they were in their teens or early twenties.
Be curious! Be bold in your choices! Try on a new identity of some kind! Try new media! Examine your old tastes and politics and prejudices! No matter how broad you already think your interests are, if you're suffering this kind of despairing frustration, they can be broader still.
You can survive this and once you get going, you might even find it's fun.
