Ah, yes, if I don't like something, it's obviously because I don't understand it.
Not necessarily, but in many circumstances, this is true. Everything that has worth to someone has a *good* reason to have achieved that worth. Understanding that reason helps you to at least appreciate something, even if it's not for you.
This becomes more true when you talk about a broader group. Anime is a pretty huge grouping of things. There are plenty of valid reasons that Anime is not someone's thing. It's not really my thing, for instance, because I have little patience for some of the archetypes, and I have a very short attention span when it comes to plot.
But there's still anime I LOVE out there, even stuff that uses those annoying archetypes or has very little forward plot momentum. For instance, FLCL is nearly a work of art, and at six episodes, it's brief. Grave of the Fireflies is historical drama, heartwrenching. Cowboy Bebop feels something like the Anti-Trek, all jaded and mistrustful of our future human selves.
There's also stuff that is very poach-able without being that awesome in my eyes. Fer'instance, InuYasha may be insufferably enduring, but the villains are interesting monsters, and the core story about hunting down a broken sacred object has "Multiple McGuffins" imbued in it. Fullmetal Alchemist is astonishingly crystal in it's take on Science Gone Too Far, and is ripe with conflicts and concepts ripe for injecting into any D&D world.
Anime is a very broad group, and it's hard to find many common threads in them. It is possible to dislike those common threads, but fifteen year old boys with giant swords and collectible monsters and pointless flexing matches are only present in some of it. There's still plenty of stuff that's awesome beside that.
So it's often very suspect when someone claims they hate all anime for X, Y, and Z. Usually, this claim is off-base enough to call defenders who say "Look, not all anime is X, Y, and Z. I really lie this one that's B, F, and Q. So you can't say you hate all anime, because my favorite has none of the traits you hate, and it's anime."
It's kind of like saying "I don't like japanese food, because I don't like sushi," neglecting the fact that there's a world of food out there that isn't sushi. Or saying "I don't like the southern USA, because I don't like racist rednecks," neglecting to note that the racist redneck is just a stereotype, not a truism.
You can still not like Japanese food, of course, but there's gotta be a good reason that actually applies to Japanese food. "I don't like most Japanese food because I'm not used to the flavors," is a good one. "I don't like the deep south because I prefer to have snow in January," isn't a bad reason for not wanting to move to the South, too.
And "Anime generally annoys me because I hate reading subtitles and the voice actors are usually horrible" is a pretty solid leg to stand on (for instance). Or saying "The anime I've seen all is drawn with the same kind of giant eyes and little mouths and it annoys me," is good, because it doesn't rule out anime which doesn't use that trope (and they do exist, they're just not common).
But saying "I don't like anime because I don't like the unrealism of spikey-haired fifteen year olds who wield six-foot chunks of steel" is as off-base as saying "I don't like the South because I don't like racist rednecks." It's a stereotype. One that you can certainly find examples of, but not one that defines the limits of what you're talking about.