I'm not sure if you want an actual explanation or advice, or if you're just venting, but I'm gonna drop my two cents. Tell me if that isn't the case and I'll delete the comment.
Judging by your signature, you have written 25 stories here in SH in the span of 2 years and a half. I am not very familiar with AO3 but if I'm understanding correctly, you have written more than a hundred stories since 2016 on that site. Most of these are novella length. I did the math and that's basically a full-length book per month.
Most of these seem to also not really be connected in any way, self-contained stories and such.
What you're feeling is burnout, something every creative struggles with eventually. Creativity is like a battery. You can try to fill it by consuming media, and spending little of it by doing what you like, but eventually, you're going to have to let it recharge naturally.
My personal advice? Stop writing for a month or two. Let the ideas take root in your head. And when you come back, try to write something longer. Make it a trilogy, just to give you an example. Do some worldbuilding, plan long character arcs, etc. Give yourself time to get invested in what you're writing and the characters you designed. I don't think it is an issue of passion, clearly, you have it considering your body of work, i think it is an issue of investment.
Like I said, just my thoughts. I may be plain wrong, but i believe that is what's happening here.
