I agree having two templating systems is a problem (more on this later) but by going SPA your front end now becomes massively more complex than sprinkling some

I agree having two templating systems is a problem (more on this later) but by going SPA your front end now becomes massively more complex than sprinkling some JS here and there. For example you now need to manage application state which is not a trivial problem on large projects. You also need to replicate native browser UX if you're serious about making a good SPA (eg: your forms are filled when going back, the content and scroll position are preserved when going back, etc). As for the duplicate template problem, this is easily solved by doing SSR + hydration. I concede this is generally complex to set up (unless using something like Next.js) but it's worth it IMO. It's really the best of both worlds (MPA vs SPA). You are still creating components and having a sophisticated interactive UI just like in the SPA world, but front end development is greatly simplified since you're only dealing with one page at a time. Also, in many cases, you might not even need an API. How many times have you create an API only to feed your SPA? It's a lot of overhead. Also these days I don't think the decoupling argument is so strong unless you're working on a complex project with multiple teams.