I agree with There Will Be Blood. It wasn't bad, but I couldn't get into it.
Similarly some of the most critically-acclaimed superhero films that I found okay but not great, especially The Dark Knight (I loved Batman Begins) and Black Panther. The Dark Knight is the main reason I avoid reviews before seeing a film - I'd loved pretty much everything Christopher Nolan had done up until then, so was excited enough without seeing the gushing reviews. Maybe my expectations were too high.
2046 was a highly-rated romance (and supposedly sci-fi) that bored me.
Anomalisa, an animation about a guy bored with his life, got great reviews, but I thought it was terrible - another really boring film.
Lady Bird, a recent critically-acclaimed film - I couldn't empathise with the main character and was bored throughout the film. Speaking of redheads, Run Lola Run bored me too.
Magnolia, Requiem for a Dream, Fear and Loathing in Las Vegas, Amores Perros, Goodfellas, The Hurt Locker, Computer Chess, The Boat That Rocked, The Fault in our Stars, American Beauty, Dr. Strangelove, Brazil, Summer Wars, Chicken Run (I loved previous Aardman animations), The Departed (not a patch on the Hong Kong original), District 9, Control (the biopic about Ian Curtis), Reservoir Dogs, Ran (the 80s Japanese film) and What We Do in the Shadows all bored me.
I love Studio Ghibli, but probably their most loved film - My Neighbour Totoro - is one of my least favourite Studio Ghibli films, though it was okay. I didn't like Ponyo much.