Bedrockgames
I post in the voice of Christopher Walken
I ran an Eberron one-shot a few months ago. A few months before that, I ran a 10-session adventure that ended when I moved out of state. Since then, I've just been trying to come up with something believable for a long campaign.
I can link scenarios well, but lately I've been overly-concerned with D&D cliches and shallow NPC motivations. When I write, i intially think the idea I'm working on is interesting, but soon find myself thinking "this is lame", or "nobody would do that", and I scrap the idea.
Maybe I'm struggling with complexity.
The first campaign I ever ran was deep, complex, and dramatic. My players still regard it as their favorite. Minimal railroading - but the NPCs felt real and vibrant. Their goals made sense. The world was vast. The problems were believable.
I seem to have trouble achieving that level of maturity in my recent works.
Okay. I think the issue may be that you are overly critical of your material. This happened to me at one point. Where I had a series of really, really excellent campaigns, and I got it into my head that everything I did needed to be good enough to bronze for the ages. Once I started thinking this way, it stifled my creativity. It wasn't until I gave myself permission to just prepare, no matter how mediocre or uninspired the stuff seemed, that I started getting creative again.
Also, keep in mind, your players probably won't really notice. In my experience, the stuff that I thought of as mediocre, the players really liked. In fact, once I allowed myself to be a little less original with my adventures, I think the players had more fun, because I was more focused on what worked game-wise than on what made me feel proud of my creativity.
So my advice. Just prepare material, don't worry about how original or cool it seems. You just need to get back into a flow. Once your not thinking so much about it anymore, inspiration will come.