There is a very definite skill in writing a suite of useful tests. You can't approach it as a "check the box" exercise.

Automated testing allows a huge range of repeatable tests to be applied quickly. My first engagement with a professional tester was a humbling experience. I take pride in my work and do put a lot of effort into my code but the tester found gaps I simply hadn't thought of.

The thing is that over time the knowledge of what is required for testing is absorbed and results in a more rich set of automated tests.

I see UAT as separate to QA. UAT should be about the useability of a system rather than a "flush out the bugs".