It’s definitely hard to build big projects this way. It’s great for quick hacks, but the more complex the system, the more it (or any current LLM-based system) will struggle. I have other rants about the pricing model elsewhere on here but I won’t repost those just now.
I have just written a very lengthy post specifically about how to make the most of Cursor for larger projects though. It’s about a 6 minute read. There’s also a section about TDD in a reply for good measure if you’re interested: An Idiot’s Guide To Bigger Projects
As always, your mileage may vary, but there might be some things in there that could help.