I'll try adding to the conversation by at least justifying why I like SPAs: clearly decoupled front-end/back-end logic, likewise parallel updates/deployment from different teams, back-end mocking, minimal data updates for DOM changes, easy integration with microservices, powerful front-end tools to deal with client feature creep (e.g. interactive widgets), reusable UI components, easy migration to multiplatform desktop apps (e.g. Electron), possible single language for everything (JS, rather than a mishmash of JS/HTML/CSS/Python/PHP/etc), easy integration with hybrid or SSR stacks ( Next.js, Gatsby, etc).

But all this is just rationalization for one simple fact: I'm vastly more productive building SPAs. I know the tools, and I can quickly deliver anything from simple sites to richly interactive experiences very quickly. I can go from SPA -> SSR (via, say, Gatsby) easily. But going the other direction from SSR to something interactive has been far more painful for me. That's why I default to SPAs and adjust from there.