There are many web apps that make zero sense to write a native app for. For example, my company's product is an LMS - the administrator side is not something that makes much sense to make a mobile app for iOS and Android, as one has to create/manage courses, manage users, and view useful displays of data (i.e. charts). Instead, we have a web app that degrades acceptably for mobile, losing such features as multiple selections for modification (it has a lot of grids).
For such an app, having a longer load upfront in order to facilitate vastly better UX than using purely server-side rendered pages is a huge win for our customers, and having the time to load & interact being low also adds tremendous value to the customers, to the point that they flock to us over our competitors.
I don't find myself having a problem with frontend web app architecture - most of the problems out there are already solved or solvable with a little time spent on thought, but the knowledge is not widespread, and so we have a lot of people who have never seen what good structure looks like.