I think there are two broad cases where ai coding is beneficial:

1. You are a good coder but working on a new (to you) or building a new project, or working with a technology you are not familiar with. This is where AI is hugely beneficial. It does not only accelerate you, it lets you do things you could not otherwise.

2. You have spent a lot of time on engineering your context and learning what AI is good at, and using it very strategically where you know it will save time and not bother otherwise.

If you are a really good coder, really familiar with the project, and mostly changing its bits and pieces rather than building new functionality, AI won’t accelerate you much. Especially if you did not invest the time to make it work well.