It's very weird that you would reach for Lacan and Chomsky. Neither of them are really seen as credible in the field of philosophy, nor have they had really large impacts in philosophy. Cultural criticism and linguistics? Sure, I guess. But not in philosophy. Even in the 20th century "continental" tradition of cultural criticism, Lacan is not very high in the eyes of many. Heidegger (controversially, of course) or Maurice Merleau-Ponty or Paul Ricoeur have been much more influential. For whatever reason, Lacanian analysis did burn bright in the 70s and 80s, but man has it fallen hard.

Arguably all modern philosophy of language in the 20th century was influenced by Ludwig Wittgenstein. Wittgenstein is, for many philosophers, the most influential philosopher of the 20the century. Wittgenstein's "method" and work in Philosophical Investigations also offers the most far reaching and consequential criticisms of platonism, cartesian mind-body dualism, and philosophical skepticism, in the philosophical canon.

I do agree with your closing comments though. Most people aren't very well versed in philosophy and operate on a sort of pop understanding of it. They simply lack the framework to make credible claims on the usefulness of it in general. It's especially hilarious when they try to say one of the longest and most fruitful intellectual disciplines in human civilization is "not very useful." Sure, bud.