If you want better tests with more cases exercising your code: write property based tests.
Tests form an executable, informal specification of what your software is supposed to do. It should absolutely be written by hand, by a human, for other humans to use and understand. Natural language is not precise enough for even informal specifications of software modules, let alone software systems.
If using LLM's to help you write the code is your jam, I can't stop you, but at least write the tests. They're more important.
As an aside, I understand how this antipathy towards TDD develops. People write unit tests, after writing the implementation, because they see it as boilerplate code that mirrors what the code they're testing already does. They're missing the point of what makes a good test useful and sufficient. I would not expect generating more tests of this nature is going to improve software much.
Edit added some wording for clarity