That #1 on the list is SWF as a single file is really, really stupid. People
can author standalone SVG or embed their scripts directly into HTML, they just choose not to. About half the problems of modern Web development practices are not that such-and-such makes something impossible, it's that people pass up what's possible (even what's sensible) in favor of the monkey-see-monkey-do style of development that involves dumping Dockerized Webpack Babel Rollup TypeScript Bazel React projects transpiled from Clojured Elixir onto GitHub with three quarters of a gigabyte of NPM dependencies.
It's nonsense to say that "HTML5/JS has [...] gotten worse". It's not a vendor SDK where platform version X doesn't support feature from version because the platform hired a new head of the design team who wants to shake things up by ditching the previous gen for the new shiny that you have to use instead. Web platform standardization is additive. If the new stuff sucks, don't use it, and keep doing things the "old" way. Don't do dumb stuff like trying to stay on the bleeding edge for no good reason and then complain when you get cut.
It's also a total contradiction to double back after all of this and try to claim that HTML5/JS is "programmer-centric". To go further and say that "Flash was content-first" is something all on its own. Standard web tech is content-first in a way that Flash never was, or more accurately, it's user-first. Flash on the other hand was always creator-first, prioritizing authors'/designers' pixel-perfect vision over users and accessibility, and the tacit endorsement of the worldview that the ends justify the means and that it's okay to favor blobs over, you know, content—which is ironically exactly what's wrong with the current world of SPAs driven by inscrutable minified bundles on the order of megabytes just to do something like put half a dozen form controls on a page that still doesn't manage state correctly.