I have the same opinion. Building SPA is f* hard and time-consuming. But it depends. If you know how to build SPA fast, then, by all means, go that route. (As a solo dev or small team) I use Rails, but Rails views are a disaster. You can use a lot of different patterns/gems, but still, logic is highly coupled with the view layer. Personally, I like Phoenix approach with templates + views. But still writing script tag…
Take this with a grain of salt, as I only recently came across it and haven't used it, but the Trailblazer framework looks like it has a good way of getting logic out of the views.
For example maybe an Order only needs a price when it's created, but needs a invoice number (and some other validations) when marked as paid, but an admin should be able to override those validations at any stage. If you are doing something like that with standard Rails the model is going to end up as an untestable mess, where as the form objects can be tested on their own.
My only complaint is that the creators of Trailblazer really don't seem to like Rails, so trying to get them to both work together can sometimes be a bit tricky. And the documentation is lacking if you want to do some more complicated things.