It's usually one of two things. First, I say I want to build this system solving this problem with these requirements, what do you suggest? It suggests X, then I say, "Hmm, why not Y?" and it goes, "Oh yeah, Y is better," etc.

It's similar to the situation where you ask whether you should walk or take the car to go refill the car with gas. I feel LLMs have a linearity embedded in them that prevents them from finding non-linear, smart solutions, especially when data is scarce. They can probably get it done, but with far more complex solutions, which increases the risk of ending up with a crazy complex codebase when it could have been much simpler and more elegant.

The other situation is when I spot a problem or a feature change that's needed after experiencing the product, and I ask how to change the codebase, it suggests something, I say "why not this other thing," and then we do the other thing.

It’s a tool that does what you want not an opinionated senior dev. Ask it to research and do an evaluation on the pros and cons of choosing X over Y and it will do a fair job.