Not sure how that helps users like me, but had you told me 20+ years ago that this was going to be “the state of the art” when it comes to app management (by two of the biggest tech companies in the world) I would have called you crazy. And I was a Windows 2000 user back in those days.
It’s also funny that, in a way, the WhatsApp app was the one that nuked itself. The “full storage” issue had been caused by some of my friends sending constant photos and videos of their cats (and one guinea pig) via WhatsApp, storage gets full, iOS decides to offload the WhatsApp app, I get left out of the app once I’m not allowed to “reload” it anymore. Again, crazy to think that this is the state of the art in app management.
"Want to sideload apps? No problem, just pay us $99/year for temporary installation privileges!"
"Want to sell your app? Here, just give us 30% of your proceeds."
"Running out of storage? Here's a red-dot notification in your Settings app begging you to pay for iCloud."
I don't think any of these companies will (or should) get out of this antitrust litigation unscathed. The amount of control all of these platform-holders exert is unreasonable, and unless the government steps in we're helpless to stop it.
You can – unless the application publisher decides to disable this. It sounds like Facebook disabled your ability to install an older version of WhatsApp that supports the version of iOS you are running. All it would take for this to work for you is for somebody at Facebook to tick a single box that allows their users to do this.