At least for me your message is very valuable, because the recognition in everything you say makes me feel less alone, or weird for that matter.
I quit my job just short of a year ago and took some time off. To some extent, it was helpful, because leading up to my quitting I noticed that I found it harder and harder to deal with even simple dilemma's or interpersonal issues. I felt myself steadily getting weaker, less resilient, and more isolated.
Leaning into that isolation, at first, helped. Having saved up some money I also didn't have to worry about, well, anything basically.
But at least in my case I feel I let it last a bit too long. The lack or purpose, even a 'stupid' purpose like showing up for a job I hated, ultimately made me feel terrified and the resulting existential 'depression' was possibly worse than barely-managed lifestyle I had before.
For the past few months I've started engaging again. I try not to ask myself too often what the 'point' is, but rather I try to dip my toes into different things, in the hope that I can find something that pulls me in so much that I stop dwelling on myself and 'big questions'.
I'm also considering a psychologist, even though for now I think I'm in an upward trajectory.
In the end, I've come to the (tentative) conclusion that my problem is not that I cannot find meaning, purpose, fulfillment or, well, happiness. Because in the end I believe nothing 'really' matters in some objective sense. And if I believe nothing matters, why would it surprise me that I cannot find something meaningful?
But that's not the issue at all. No matter how meaningless we think life might be, I've rarely met someone who truly feels that way too. We generally don't live with full awareness of our rational beliefs. And I myself too have gotten caught up in things that, until I reflect too much, feel intensely meaningful.
Rather, my problem, or at least one of my problems, is that my inability to handle the day to day realities and my attempts to 'fit in' (even while openly rejecting 'normalcy') have kept me from losing myself in whatever 'game' is challenging and fulfilling enough to not feel like a pointless game. As a result, not only am I stuck in a perpetual state of 'this is not meaningful, I need to reassess/fix/change/improve', and simultaneously a tremendous lack of experience with the mind-boggling variety of life games there are to play.
In fact, maybe an even bigger problem is that I have the arrogance to think that there is no game that can fool me.
I've found a lot of help in being around people who do not suffer from all that introspection. They seem to just randomly try things first, and only then concoct a story and meaning around it. And partly as a result of living in this way for a long time, they have actually figured out a lot of what makes them tick, and they found that 'game' that challenges them just enough to make them feel purposeful, but not so much that it overwhelms them.
And sometimes I think one good solution is to do more of that.
It's like I've gone through much of life trying to find that right partner without actually trying out relationships. The result is that I have spared myself the trouble (mostly) of broken hearts, mistakes, and terrible breakups, but I've also kept myself from actually figuring out what kind of relationship fulfills me. Because you can't really figure these things out without doing them.
I suppose mostly I'm just expressing my own process/issue in the hopes it helps someone feel less alone in their struggle. I don't think any of what I'm doing is necessarily a good prescription to anyone else.
Ultimately I find that at least one things that drags me out of depression is to focus on the trouble of others, or to swap stories. It doesn't solve things long-term, but I think it helps. The only thing I find worse than depression is feeling alone.