I'm not discounting your experience, but purely from experiment design, you don't have any sort of pre/post AI control. You've spent 3 years becoming a subject-matter expert who's building software in your domain; I'm not surprised AI in it's current form is helpful. A more valuable comparison would be something like If you kept going without AI, how long would it take someone with similar domain experience who's just starting their solution to catch using AI?

According to many conversations I’ve had or observed on this site, plenty of people will be surprised if not doubtful.