There’s definitely more to existentialism than that. I don’t think any two existentialist philosophers are alike. Kierkegaard, Sartre, Camus, Heidegger, Watsuji, Nishida, Nishitani, et cetera. None of them are remotely similar other than in being existentialists. It makes sense though, for a school of philosophy that rejects essentialism to be so disparate in ideas.

I do like Schopenhauer, though. So much better than Nietzsche who kinda stole his thunder.