I think it's even less important for startups.

At some point, the business cannot be just one app or one tech stack. More devs will come aboard that disagree with the chosen tools and for very good reasons. You must work with the devs you have and the expertise they bring. Only the most out of touch CTO would avoid sunsetting legacy apps. There's the business side concerned with functionality, and then there's the hiring side concerned with implementation details. Both are key to getting the best devs and the best results.