I suspect you're a junior engineer if you think that way. Domains (any) are deep, and require thorough understanding before you can have business or revenue impact.
I agree that domains are deep but rarely I'll touch all areas of the domain in any given role. As I mentioned in other comments, I don't have to know all of it, as there are other people in the business and likely within my team who:
- probably don't know 100% either; but
- know things that I don't
We work together so as a team we have as broad and deep a domain knowledge we can for the needs of our products and projects.