This is definitely a step in the right direction. Problem isn't the browser's ability to run code such as JS which makes it possible to create things like supercookies. Problem is web pages are effectively applications that are semi-local (they can bind to local resources such as cookies, caches, storage, and connect to local peripherals) and the security model is very different between viewing HTML documents and running untrusted apps.
No good comes from downloading random, untrusted native applications from the net, installing them locally, and trusting these not to infect your system with malware. No good comes from loading random, untrusted applications into your browser either, and trusting these not to infect your browser, either.
Basically everything on the web should not only be sandboxed with regard to local system (this is mostly established) but also be sandboxed per site by default. Hidden data, or anything that's not encoded in the URI, should only move between sites at the user's discretion and approval.
I've had personal plans to ditch my complex adblocking, multi-account/temporary container and privacy setup in favour of a clean-state browser that I launch in a file-system sandbox such as firejail for each logical browsing session (like going shopping for X, going online banking, general browsing). Basically an incognito session but with full capabilities as sites can refuse serving incognito browsers. Normal browser setup with everything wiped off when the browser exists.
I have some dedicated browsers for things like Facebook where I whitelist a handful of necessary cookies and forget the rest on exit. This, however, won't clear data other than cookies. I think that per-site sandboxing would mostly solve this problem. I don't particularly care what data each site wants to store on my browser as long as it won't be shared with any other site.