What you're describing is "existentialism", and Camus's absurdidm is a reaction to it. The difference is subtle, but important to Camus.

It's been a very long time since I studied it, so you're likely right... but I thought that existentialism was the problem statement (life has no inherent meaning so we bring our own) and that absurdism and nihilism were both responses to it?

My understanding has always been that Absurdism says that while the search for meaning is absurd we should search anyhow if we feel like it (our happy friend Sisyphus). Whereas Nihilism's answer was more along the lines of Bukowski's "Don't Try." They both recognize that Sisyphus's job is pointless, but the absurdists suggest we keep pushing the boulder anyhow.

Am I missing something?