I too sometimes wish I'd been an English major, but not because I think it would've been easier. Not to be condescending or mean or anything, but I sort of think of college as a time when you get to study the things you love, the things you're passionate about. If the reason why you like the class isn't because you're "a big fan of poetry" but because you're a big fan of "an easy A," then maybe you're not making the most out of the classes that you take. In the long run, in a cosmic sense, easy A's matter less than spending your precious few college years doing things that you *are* a big fan of. Don't get me wrong, I highly encourage people to study poetry even if they aren't already "big fans," since everyone was a non-fan before they became a fan, and I don't like it when people act all elitist about poetry as though it weren't created as a gift for the masses. I just think that with an "easy A" mindset, you might not be getting as much out of your classes as you could be.
And I think the reason why many English classes give you full credit for an answer as long as you back it up is not because they're dupes but because they're trying to train you to think originally, the way that people who make a living as literary critics and poetry scholars think. Coming up with an original interpretation that you can defend is just as important a skill as regurgitating facts on science tests that aren't graded "arbitrarily"; it's how knowledge is furthered in the humanities. Please don't treat your English exams as a chance to trick your professors into giving you "easy A's" for writing BS, just because you can get away with it; instead, put down answers that you believe in, because you owe it to yourself.
In the long run, even in scientific fields, your success won't be evaluated objectively and non-"arbitrarily." Some day when you're a PI, you'll have an idea for an experiment and another PI will have an idea for another experiment, and no one's going to be assigning you objective, non-"arbitrary" grades to tell you whose idea is more valuable. Just like answers to essay questions on English exams, things like that can't be measured objectively, either. I think that's just the way the important things in life are.