I will not promote

I'm interested what are common pain points when building MVP, any horror stories how early tech decisions derailed your growth in future? for example I worked in really promising startup who managed to raise good money but their original dev team made some terrible architecture choices, so when they replaced them with me and few other really competent colleagues it took us almost 2 years to get it back on track, but it was kinda too late for the product at that point sadly. Missed on some good equity and I often think how much more we could have done if only CEO hired decent devs to begin with.