Creating new software is far more than just a matter of tokens. LLMs are like a small programming team: you still need a project manager (you!).

And tax return software is a perfect example of where "vibe coding" will go horribly wrong: a superficial tax return is trivial; handling tax rules for every different situation is vastly more complex. (1) You need to codify all the tax rules; (2) You need to do it reliably (which means really understanding how to work with LLMs: harnesses, gates, verification, reviews, etc.); (3) You need a corpus of real-world examples (taken from where?); (4) You need user feedback.

This would be an intensive multi-month project. And that's before even looking at marketing and sales.

Can a competitor race with you? Sure, but only if they're also determined to put in the work.