These people definitely have an overly rosy view of the past. The sites that are dog slow shit ux now still would be with server rendered html and jquery spaghetti, just like they were in the past.
Ever submit some giant form to get some random error and then lose the entire state of it? Used to be extremely common, even though it shouldn’t have been.
Losing the entire state happens on SPA. Plus a random error not providing any feedback is a typical SPA experience. You can poorly execute on any technology. It's just much easier to do things wrong using this-year-trendy-SPA-framework.
Use the appropriate technology, everything doesn't have to be a SPA.
And yet it used to be much more common. SPA or not doesn't change how your team executes, what kind of management you're working under, or any other externality that makes you end up with a shit website.
Ever submit some giant form to get some random error and then lose the entire state of it? Used to be extremely common, even though it shouldn’t have been.