After reading the comments, I must be the only person in the world who misses good, old-fashioned Rails templates / views. With someone who knew the internals well, they were a productivity gold mine.
That's still a valid way of doing development, but it doesn't really work for a SPA. You may not want a SPA, but if you do, you pretty much need something like Angular/React/Vue.
It would still be a valid way of doing development, if teams weren't cargo culting frameworks for tasks that really don't need them. I can't begin to tell you just how annoying React is for making a CMS.
i love using flask, jinja, and jquery, but as i start to create more dynamic interfaces with this pattern both the pitfalls of it and the appeal of things like react and vue are making themselves apparent. think it may be time to sit down and have a go at vue.
Recently there's a push to eliminate jQuery usage from our codebase, and it's highlighting just how much React doesn't do for you. jQuery, for all it's faults, has been maturing for 10 years or so. It makes a pretty good footgun, but it's not like I've never seen anyone shoot themselves in the foot with React either.