It's a little misleading to say that philosophy is useless. You can get that feeling by looking at what's called philosophy today, but that's because branches of philosophy that became useful are now called something else.
Many useful studies started out as branches of philosophy. As a topic develops standards of evidence, it tends to calve off from philosophy. So natural philosophy turned into physics, biology, astronomy, etc. as practitioners got serious about observation and modeling. Likewise, logic and geometry grew into mathematics, parts of epistemology turned into psychology, and social theory is turning into social science. Today psychologists and evolutionary theorists are starting to take a fresh look at questions in ethics and aesthetics.
What's left in the philosophy department, then, are topics that have been hard, so far, to get purchase on. If you focus on these topics, you can get a feeling of futility, but it's like staring at the bare patch in an otherwise fertile garden.
Many useful studies started out as branches of philosophy. As a topic develops standards of evidence, it tends to calve off from philosophy. So natural philosophy turned into physics, biology, astronomy, etc. as practitioners got serious about observation and modeling. Likewise, logic and geometry grew into mathematics, parts of epistemology turned into psychology, and social theory is turning into social science. Today psychologists and evolutionary theorists are starting to take a fresh look at questions in ethics and aesthetics.
What's left in the philosophy department, then, are topics that have been hard, so far, to get purchase on. If you focus on these topics, you can get a feeling of futility, but it's like staring at the bare patch in an otherwise fertile garden.