I still like Naval Ravikant’s definition from his extraordinary guest spot on the Farnam Street podcast[1]:
“Today, I believe that happiness is, it’s really a default state. It’s what’s there when you remove the sense that something is missing in your life. We are highly judgmental, survival, and replication machines. We are constantly walking around thinking I need this, I need that, trapped in the web of desires. Happiness is that state when nothing is missing. When nothing is missing, your mind shuts down and your mind stops running into the future or running into the past to regret something or to plan something.”
If it were the default state would people find it so hard to attain? It's hard not to want things, to not believe that there's just one more thing that could make things better. If it were simple it wouldn't be the core basis of so many religions.
I'd say the core basis of at least Buddhism is basically in line with Ravikant's thinking.
And based on my experience with Christianity, much of Jesus' teaching, while not exactly the same, also emphasizes practicing not wanting things ("See the birds of the sky, that they don’t sow, neither do they reap, nor gather into barns. Your heavenly Father feeds them. Aren’t you of much more value than they?")
I wouldn't be surprised if this thought is a core element of most religions. Of course, religions are messy, so you're not entirely wrong either.
[1] https://fs.blog/naval-ravikant/