I have very often seen people criticise Philosophy from a point of ignorance and then follow up by espousing their own very bad philosophy. It's kinda like criticising a Mathematical proof without understanding Math. You can do it, but you're highly likely to be off the mark.

It's not that Philosophy doesn't have areas worthy of criticism. I personally believe that the best reason to study metaphysics is to learn why metaphysics is useless. Ironically, understanding why it's useless is actually quite useful :o)