Tiktok has nailed the delightful "stumble upon" effect of getting users of all ages to keep going to the next and the next video. I don't mind how each new piece of content is paged because the content is better for the format and it doesn't feel clunky when I do want to skip to the next one.
Instagram couldn't switch their algorithm because people think they still want to see the content they've been seeing... otherwise they'd just be using TikTok.
In insta, we are used to scrolling really quickly until something catches the eye and THEN we engage. That is because the content in the insta feed is not as good and there are more ads. The new scrolling/paged UI in Instagram feels terrible because I can't fly through bad content to engage with what I want.