I think that when you “poison” your brain with easy dopamine like candy, fastfood, alcohol, drugs, endless scrolling, etc you will shift the internal goalpost of when something feels good. Compared to these easy sources of “joy”, life just isn’t that interesting. The scale changes to the point that normal things cannot longer provide enough jou to be worth it.

Personally I’ve been trying to constrain myself a bit on these easy sources of “empty happiness”. Things that do give me joy without ruining my brain are, among others: running, music festivals, listening to nice music, looking back at something cool I made, making something cool, playing videogames, chilling with friends (though this usually involves alcohol). These things definitely don’t reliably provide joy, Most of the times they’re just “nice” but definitely not amazing. But every now and then I get hit with that dopamine rush and it’s all worth it.