How many coats can I realistically put on if I'm still not happy with the finish?

Painting an internal white wall with a Dulux white refresh paint that is a combined primer and paint. Its meant to be possible to get a good finish with 1 coat of this stuff but after 2 coats, it still looked patchy and uneven. I did one more coat and I'm still not happy with it. Where do I go from here? Feels like 4 coats of a paint that's meant to work with 1 coat is mad. Thinking I might need to get a pro in.