But tbh I can't really imagine any scenario that is near impossible - except for WASM driven web pages which will break just about anything :(
Flash was at least easy to decompile. The decompiled code was so good most of the time that you could compile it back into a working swf, with modifications if you want any.
But then both WASM and Flash have to get the data from somewhere. That is usually something resembling an API endpoint that returns the result in XML or JSON. Why not sidestep the whole client app thing and go straight for that API endpoint?
BTW: were you around in the days of Flash? Because it broke accessibility and a whole host of other features the same way, yet it was still used and hugely popular (there was also ActiveX, which worsened things even more). It began with online games and graphics-rich pages, but it evolved frameworks for generic apps (ie. Flex) and then even CMS engines. Soon enough Flash was used for even blogs and e-commerce. The situation today is different due to the Web having evolved into a more capable and standardized platform, but there's no shortage of devs who would welcome the ability to run their app in the browser, but who dislike HTML/JS so much they would do basically anything just to not have to touch it - accessibility and a lot of other things be damned.
Don't underestimate how irrational people and even whole communities can be.
As a bonus, here's an example of the "almost" part: http://35.158.218.205/experiments/webDOOM/
It was eventually abandoned.
Two things make this vastly more difficult now:
1. Twitter uses obfuscated css classes that appear to change on every deploy, which makes scraping hard.
2. You used to be able to get around the limit on bookmarklet code size by adding a script tag to the page and loading remote javascript. Now browsers respect HTTP headers that sites can use so that only scripts from whitelisted sites are loaded.
I could see using a set of standard tweets you created to sort of benchmark the change.
% curl -s https://manifold.markets | htmlq '#__next > div > main > div.items-center.flex.flex-col > div > div.gap-8.flex.flex-col > ul > div > div > div > div.relative.flex-1.gap-3.pr-1.flex.flex-col > div.peer.absolute.-left-6.-top-4.-bottom-4.right-0.z-10 > a'
will get you all the anchors for the stories on the home page, and from there it's easy to get any other part of the stories.
www.google.com##div[role="heading"]:has-text(/^People also ask$/):upward(5)
www.google.com##span:has-text(/^People also ask$/):upward(5)
www.google.com##div[role="heading"]:has-text(/^Cast$/):upward(5)
www.google.com##span:has-text(/^Cast$/):upward(5)
www.google.com##h3:has-text(/^Videos/):upward(5)
www.google.com##h3:has-text(/^Images/):upward(5)
www.google.com##div[role="heading"]:has-text(/^People/):upward(5)
www.google.com##span:has-text(/^People/):upward(5)
www.google.com##h4:has-text(/^People/):upward(5)
www.google.com##span:has-text(Related searches):upward(5)
www.google.com##span:has-text(/^Latest/):upward(4)
www.google.com##h3:has-text(/^Top stories/):upward(6)
www.google.com##div:has-text(/^Trailers/):upward(4)
www.google.com##g-scrolling-carouselYou'd probably think it'd be simple, right? This being the kind of thing that Cascading Style Sheets were designed to handle elegantly and gracefully?
https://maya.land/user-styles/youtube/
I always thought people on here were just cranks complaining about style bloat, because a lot of the "this could have been a text file" arguments were applied to things that were genuinely better with the presentation polish. But this? How can developer ergonomics be worth this?
Anyway, user styles and user scripts and bookmarklets are all great and I use them all the time. This level of Big Tech deformation of the basic web technologies makes them more annoying, but still not impossible.