There's a lot of programming propaganda that floats around and gets amplified that talk up the advantages of some approach. Often the advantages being discussed aren't even the
outcome of the technology, they're just the
goals of the technology. Said propaganda will also completely fail to include the disadvantages of the approach. The result is a whole bunch of people who will flock to the new tech, and only 2 or 3 years later will the real story start to come out. The tech usually does have legitimate uses, it's just those uses were
niche rather than "everyone should do it this way".
A big recent non-web example of this is NoSQL databases. Endless hype about their advantages. Virtually no discussion about their disadvatages. (In relative terms. It was actually there in absolute terms, I know because I picked up on it. But it was buried for a couple of years in the hype.) Endless hordes of developers switching to them, and confirmation-biasing their way past the first few red flags. Do they have a niche? Yes. Were they massively, massively overused? Absolutely. I've seen projects killed by the choice to use them, and many others switch away from them in a tearing hurry because their systems were coming down around their ears. Would a lot more discussion of their disadvantages been helpful? Who knows. In the midst of a hype cycle sober engineering discussions become a form of betrayal or personal attack for a whole bunch of engineers who too-quickly incorporate the new tech into their personal engineering identity.
SPAs are the same way, and more generally, heavily REST-based backends. Is there a time and a place for them? Absolutely! Are they always the best default organization? Heck no. Do they come with a lot of costs that need to be accounted for with the benefits? Yes.
Stepping up to a stratospheric level of abstraction, outright philosophical astronautics here, I think one of the biggest mistake programmers make is to sit down at some technology decision in which one must weight the costs or the benefits, and implicitly without thinking about it, assign a flat ZERO to some tech's costs or benefits. Most often costs, though the latter can happen. Especially in their earlier years, though even older programmers can get caught up in a hype cycle if they're not careful. Costs are never zero. Benefits are effectively never zero because nobody talks about techs with no benefits at all.