There are things I know I learned from studying philosophy. The most dramatic I learned immediately, in the first semester of freshman year, in a class taught by Sydney Shoemaker. I learned that I don’t exist. I am (and you are) a collection of cells that lurches around driven by various forces, and calls itself I. But there’s no central, indivisible thing that your identity goes with. You could conceivably lose half your brain and live. Which means your brain could conceivably be split into two halves and each transplanted into different bodies. Imagine waking up after such an operation. You have to imagine being two people.
The real lesson here is that the concepts we use in everyday life are fuzzy, and break down if pushed too hard. Even a concept as dear to us as I. It took me a while to grasp this, but when I did it was fairly sudden, like someone in the nineteenth century grasping evolution and realizing the story of creation they’d been told as a child was all wrong.  Outside of math there’s a limit to how far you can push words; in fact, it would not be a bad definition of math to call it the study of terms that have precise meanings. Everyday words are inherently imprecise. They work well enough in everyday life that you don’t notice. Words seem to work, just as Newtonian physics seems to. But you can always make them break if you push them far enough.
I would say that this has been, unfortunately for philosophy, the central fact of philosophy. Most philosophical debates are not merely afflicted by but driven by confusions over words. Do we have free will? Depends what you mean by “free.” Do abstract ideas exist? Depends what you mean by “exist.”
Curiously, however, the works they produced continued to attract new readers. Traditional philosophy occupies a kind of singularity in this respect. If you write in an unclear way about big ideas, you produce something that seems tantalizingly attractive to inexperienced but intellectually ambitious students. Till one knows better, it’s hard to distinguish something that’s hard to understand because the writer was unclear in his own mind from something like a mathematical proof that’s hard to understand because the ideas it represents are hard to understand. To someone who hasn’t learned the difference, traditional philosophy seems extremely attractive: as hard (and therefore impressive) as math, yet broader in scope. That was what lured me in as a high school student.
This singularity is even more singular in having its own defense built in. When things are hard to understand, people who suspect they’re nonsense generally keep quiet. There’s no way to prove a text is meaningless. The closest you can get is to show that the official judges of some class of texts can’t distinguish them from placebos. 
And so instead of denouncing philosophy, most people who suspected it was a waste of time just studied other things. That alone is fairly damning evidence, considering philosophy’s claims. It’s supposed to be about the ultimate truths. Surely all smart people would be interested in it, if it delivered on that promise.
The field of philosophy is still shaken from the fright Wittgenstein gave it.  Later in life he spent a lot of time talking about how words worked. Since that seems to be allowed, that’s what a lot of philosophers do now. Meanwhile, sensing a vacuum in the metaphysical speculation department, the people who used to do literary criticism have been edging Kantward, under new names like “literary theory,” “critical theory,” and when they’re feeling ambitious, plain “theory.” The writing is the familiar word salad:
Gender is not like some of the other grammatical modes which express precisely a mode of conception without any reality that corresponds to the conceptual mode, and consequently do not express precisely something in reality by which the intellect could be moved to conceive a thing the way it does, even where that motive is not something in the thing as such. 
The singularity I’ve described is not going away. There’s a market for writing that sounds impressive and can’t be disproven. There will always be both supply and demand. So if one group abandons this territory, there will always be others ready to occupy it.
If it seems like a daunting task to do philosophy, here’s an encouraging thought. The field is a lot younger than it seems. Though the first philosophers in the western tradition lived about 2500 years ago, it would be misleading to say the field is 2500 years old, because for most of that time the leading practitioners weren’t doing much more than writing commentaries on Plato or Aristotle while watching over their shoulders for the next invading army. In the times when they weren’t, philosophy was hopelessly intermingled with religion. It didn’t shake itself free till a couple hundred years ago, and even then was afflicted by the structural problems I’ve described above. If I say this, some will say it’s a ridiculously overbroad and uncharitable generalization, and others will say it’s old news, but here goes: judging from their works, most philosophers up to the present have been wasting their time. So in a sense the field is still at the first step. 
He is mostly correct. He is wrong about the claim made about formal logic (not quoted above).