To summarize 15 years of experience for you: You keep learning non-stop the entire time and after 15 years, you've got a really good high level view and you've built up an intuition for how to separate code in a way to minimize complexity whilst maximizing maintainability, reliability and performance... But you still miss stuff, miss some security vulnerabilities; because complex projects give you so many things to think about, it's a struggle to attend to everything. The one real advantage is that what you miss is generally easy to fix (thanks to your design intuition).
Even after 15 years, though, my feeling is that I'm still not skeptical enough. Solving problems with software is really hard. The more experience I have, the harder it appears to be. I'm a much better coder now than I ever was by an order of magnitude but I trust my own code less than I ever did. AI is can help a junior a lot; you just have to be humble about your output and be very critical of it.