Gmail’s basic HTML view will go to the Google graveyard in 2024
Google will send Gmail's basic HTML view sailing into the great beyond starting in January 2024, after which time everyone who uses it will be switched to the service's far more modern Standard" view. The change appears to have been announced around September 19th in a Google support article.
Though the vast majority of people use the Standard view on their PCs without question, the HTML version of Gmail has its perks. The stripped-down Gmail experience loads quickly, and users can access it even on very outdated machines or with much slower connections. Its leaner nature makes it useful in situations where the best you can muster is a 3G connection (3G died last year in the US, but still).
I'm sure the HTML version also made tracking a lot more difficult.