The “problem of existence” metamorphoses when you call it the “problem of becoming”. We are becoming all the time. The question is how and if to direct it. Put another way, what should we do, one, and why, two.
I have often found that many problems that are recondite in the extreme in the abstract can be solved if you simply begin, and assume a solution is possible. Almost invariably, you will pursue false paths. You will make mistakes, which amount to figuring out ways that don’t work. This is still useful knowledge.
And what you want–purpose, fulfillment, energy, peace–creeps up alongside you in the process of focusing on other things.
Existentialism, which might practically be called the doctrine of moral passivism (I tend to use the word “Moral” synonymously with “principled work”), amounts to a doctrine of craven obeisance to the dictates of the wider world. You get pushed and pulled, here and there, and you call the resulting queasiness “authenticity”. Bullshit. Bullshit. Bullshit.
Many of these people were sick at their cores, and wanted nothing more than to be told what to do. Hence Sartre’s lifelong support of Stalin, and de Beauvoir’s admiration for Sade.
Cowardice is not a virtue, and Exitentialism, as a whole, is pernicious precisely as a poorly constructed rationalisation for moral failure, perceptual failure, and following defensive self righteousness, all on the sides of the wrong causes.
I liked Albert Camus, because he always seemed to me like he was at least TRYING to solve real problems. The rest of them seem to have existed comfortably within a sadomasochistic vortex of principled pointlessness.
They can all be ignored. William James was, in my view, the last widely known useful philospher, and his usefulness was precisely in pointing out that “philosophy” per se–seen as separate from a more primal worldview–is useless until you are solving practical problems whose outcomes can be verified. If what you are doing can be hermetically sealed in a classroom, it is not math, and it is not useful. It is, to real world problems, what the game of Monopoly is to actually leasing real buildings. If it has ANY utility at all, it will only occur when you walk off the university campus.