You use a much smaller set of applications than websites
because websites exist.You're imagining a world where the most popular dev environment goes away, and service providers decide to use HTML forms instead of forcing me to download an app every time I want to order a pizza. That world does not exist. The apps aren't going to go away, and your security model can't be, "people just won't install untrustworthy apps."
And put things in perspective here -- we're talking about a security vulnerability that allows port scanning primarily for fingerprinting purposes. A native app can not only port scan, it can literally just make POST requests to those open ports across separate domains. The security risks we're talking about are not even remotely equivocal.
Don't get me wrong, stuff like port-scanning should be fixed in web browsers. But even with these vulnerabilities, the web is still unquestionably the safest consumer-accessible application platform that we have today. Moving applications off of the web and back onto native platforms would be setting security back half a decade.
When someone comes to me and asks how they make their phone more secure and more private, the number one piece of advice I give them, every single time, is "avoid native apps and use websites instead. Don't install Facebook, use the website. Don't install random clicker games, browse them online instead."
The web has been a major asset in my quest to get friends and family not to install a bunch of random malware on their devices. Doubly so when you throw kids and younger users into the equation. I am eternally grateful that the web is advanced enough that people can join a Zoom meeting without installing Zoom on their computer.