What they do to the end user might be different, how the pieces come together, it is always the same, unless one is doing curriculum driven development.
Forget everything about responsiveness or whatever (which I find way more valuable than the tradeoffs one makes)--the lack of tight coupling is the real win of React and similar. I mean, if you'd like you can pretty easily build a server-side React app with NextJS and still get a lot of these benefits while using React purely as a pretty-dang-good templating language.
Old school server side rendered apps are underrated and its perfectly possible to make something that looks and behaves as well as a SPA app for most things.
Even in the case where you do have a specific frontend, I contend that there's still value in the separation because it very strongly encourages (coupled with tools like, shameless plug, nestjs-data-sec[0]) the writing of very clear viewmodels where thought must be put into what exactly should be exposed over the wire in a way that commingling database objects and template logic doesn't allow.
I think server-side rendered pages are properly rated at this point, not underrated; there are places to use them but they're shrinking as other tooling get better. As an example, even I write React almost exclusively because I write React faster and with fewer errors than any templating language I see in common use except maybe Razor (and Razor implies buying into ASP.NET, which, no). React/TypeScript are hard to get wrong and easy to burn through quickly. And I would call a React page rendered through NextJS a "server-side rendered app"--but I get the feeling you would not. ;)
You are seriously overestimating complexity and novelty of most software development, while underestimating engineering in other industries. I work currently as software developer and previously in a branch of a civil engineering.
Do you seriously think that other engineering disciplines to not have those small little problems that plague us all the time in software development? They do, but they can offer their solutions based on data, not just whim. They do also have codified standards, and guidelines and certification exams.
On the other hand software development is relatively new discipline - other fields had hundred of years to mature.
EDIT: and they are catching up with rapid prototyping - it is getting cheaper and faster.
I have a feeling that some SpaceX engineers would have something to say about this after one of their rockets lands on a floating barge.
That is because you are ignoring/left out the critical last part of the phrase you quoted: "and estimate it with an accuracy of 5 to 10 days and a few thousand dollars."
This is particularly relevant because this is a direct response to the following:
> We can't even accurately estimate the cost of a complex project given our choice of tools, let alone talk about costs and ROI with different toolchains for the same projects.
Anyone engineering hypersonic missiles would easily dispute that.[1] Or submarine-capable quantum communication systems.[2] [1]https://www.nytimes.com/2019/06/19/magazine/hypersonic-missi... [2]https://www.realcleardefense.com/2017/11/04/quantum_communic...
[1]https://www.scmp.com/news/world/russia-central-asia/article/...
But maybe its hard to admit it, lower down your ego and be a bit humble. Yes, software development is a creative work, but so are all other engineering branches. And yes, we have massive issues with code, process and people quality across whole business.
Also, those mature industries routinely overrun by millions of dollars and months or years, event though they are dealing with a fraction of the complexity and the costs and techniques are well known.
Software is the only industry where you are asked to build systems that have never been built before but that are more complex than anything ever built in the history of "mature industries", on top of astronomically complex systems, and estimate it with an accuracy of 5 to 10 days and a few thousand dollars.