This was going to be an edit but it go long so this is a follow-up to my above post:
I would also say ADHD can be a genuine asset to embracing joy. Like, I forget dumb/bad/annoying things pretty easily compared to most people!
And on the flipside, looking at friends and family, it's very clear to me that the biggest bar to "embracing joy" isn't cynicism or real reluctance, let alone an enjoyment of tearing thing apart. At all. I dunno if cynicism is even top 10. What I see as the leading issues are anxiety, stress and, well, forms of PTSD, possibly OCD as well but perhaps mainly because it's so good at leading to anxiety. This is part of why I do feel some real caution is warranted with the "just let it go!" model of embracing joy - because a lot of people absolutely want to do that, but have been/are being so harried by life and stuff that they actually DO need to worry about, like are they going to make rent, is their kid or pet sick, and so on. I think when you're enjoying basic financial stability (which doesn't necessarily mean wealth, but stability, and not having to worry about income or costs much, because they're basically under control), when people in your life are healthy, when you aren't dealing with abusive people in your life (who are sometimes unavoidable because they're at work or whatever), when you don't have to deal with significant, recurrent anxiety and stress, it's just a lot easier to "embrace joy".
Like, people say money can't buy happiness - but it's a half truth. It's more like, you can take a horse to water, but you can't make him drink. But if he's by water, at least he could drink. And a lot of people aren't really "by water" in this context! If they were, they would drink! But equally some people are wealthy, healthy, safe and just have a lot of difficulty embracing joy - including some friends, and in my experience that tends to revolve around them forcing themselves to do stuff they just don't enjoy because of rules or limits they enforce upon themselves, rules that may or may not benefit them in various ways, but sure don't help with joy. I could detail a lot of examples, but I feel like there's just so much more to this than merely willing it to happen for so many people.
Again, ADHD means this is mostly not the problem I deal with, because I am very good at forgetting my troubles even when I totally should not! Masterful at it even! But I feel like for most people, that's not an easy thing, and most people who seem unable to take joy in stuff, it's because things are hard for them, or they've been messed up by stuff, not because they're failing to "embrace joy". And even where that is the main thing, often it's difficult-to-escape societal or relationship that's causing that.
Sorry I'll stop going on sophomorically now lol.