For many startups, that code that you mentioned as technical debt will be deleted en masse as the business pivots and adapts.
For startups, moving fast and getting 80% done in 20% of the time is the correct choice. It's frustrating to look at the result as a software developer, but the engineer is there to serve the business, which pays the salary. As a software engineer, I very much disliked working in engineering teams that were engineering for the sake of engineering. It quickly devolves into meaningless arguments and drama.
For startups, moving fast and getting 80% done in 20% of the time is the correct choice. It's frustrating to look at the result as a software developer, but the engineer is there to serve the business, which pays the salary. As a software engineer, I very much disliked working in engineering teams that were engineering for the sake of engineering. It quickly devolves into meaningless arguments and drama.