Of course, ‘everyone can be artist’. But wouldn’t the lack of the dramatic lead to a lesser chance of ‘making it big’?

Depends, because you’re not going to be conveying your experience perfectly anyway. It first goes through your own interpretative lens to the art, and then the art goes through the viewer’s lens. Big and dramatic emotions are easier… yes and as such may be more predictably marketable. But it’s a fickle business. Of course this is a concern only if marketability is how you measure “making it big”. We have a lot of art these days that’s easy to get into… and easy to drop. If you want world to remember you (Gogh wasn’t appreciated until after his death), you can try to convey something deeper and more complex.

I am having a hard time recalling positive experiences right now, especially ones that are “vibrant” in any way.

There’s vibrancy in deepest depression and the most boring line in the grocery store. That’s for an artist to discover. But I’m not saying you should or should not take meds. But depression tends to lead to bad outcomes, and the world is full of depressed artists who didn’t make it.