I've worked in a few startups, and it always annoys me when people say they don't have time to do it right. You don't have time not to do it right - code structure and clarity is needed even as a solo dev, as you say, for future you. Barfing out code on the basis of "it works, so ship it" you'll be tied up in your own spaghetti in a few months. Hence the traditional clean-sheet rewrite that comes along after 18-24 months that really brings progress to its knees.

Ironically I just left the startup world for a larger more established company and the code is some of the worst I've seen in a decade. e.g. core interface definitions without even have a sentence explaining the purpose of required functions. Think "you're required to provide a function called "performControl()", but to work out its responsibilities you're going to have to reverse-engineer the codebase". Worst of all this unprofessional crap is part of that ground-up 2nd attempt rewrite.