Twitter's redesign attracted a lot of negative user feedback. 15 years ago Marissa Mayer headed up product at Google, she gave talks in the Bay Area at PARC and Stanford to the HCI design community on how interstitials were used to introduce new features, train users and measure feedback.
On the web, interstitials are web pages displayed before or after an expected content page, often (to display advertisements or confirm the user's age (prior to showing age-restricted material). Most interstitial advertisements are delivered by an ad server.
The current cohort of UI/UX PMs at Big Tech firms apparently no longer makes use of interstitials 
to make gradual changes in UI and to measure UX. I wonder why?