When there's a business case for paying down the technical debt then it is worth paying down. Prematurely paying it down is no more or less than a premature optimization...only perhaps worse because it comes at an opportunity cost. In the ideal world, the technical debt is forgiven because your company grows at a pace that requires a complete rewrite. In the typical case the technical debt is forgiven because the startup's outcome is typical.

Best practices are a means to an end. StackOverflow was running production and development off of a single box well after it became "a thing." Doing so was good enough because it worked and StackOverflow's successful growth was dependent on product not getting a glossy photo on the cover of Startup Infrastructure Magazine.

Make business decisions in a business like way.

Good luck.