I also feel that the problem can be somewhat mitigated by some simple strategies and probably just one person as a focussed resource for this.
Has anyone come across a tech consultant specialising in just startup SRE? Not suggesting that tech debt is an easy problem or can be completely solved. Wondering if there's a more generally available solution.
Repeat every 3 years minimum (if viable after PMF), learn design principles, core USP offerings, remove spaghetti code and building documentation.