I partly agree and disagree.
Speed completely changes the game in a few ways. The first is identifying interests. Imagine every possible interest in a tree structure. Let's say you're into kumiko. There are so many levels of the tree to traverse to find kumiko; perhaps Skilled crafts -> Woodworking -> Japanese -> Construction without use of fasteners -> Panels and decorative elements -> Kumiko. The more iterations you can get through, the better you can match people's interests. If someone has 10 interests and each one requires many questions to determine, it can take forever to find exact interests with a system that only narrows down your interests every X videos vs. after each video.
The second is matching current moods. Let's say you just broke up with your girlfriend, or your pet fish died, or you're on vacation in Spain. A rapidly-updating system can capture those trends and get right to the heart of them in time for them to matter. A slow system might only get through a few iterations and capture a vague interest in Spain; a fast-updating one can get through countless iterations of guessing. Spain? What city? Tourist or moving there? What type of tourist? Foodie? What type of food? How fancy? Bam, you're watching the perfect video about an upscale seafood restaurant in Barcelona.
The third is type and flavor of content. Even inside of a small niche you will find many flavors of content. Super-short or long form, fast paced or slow, funny or serious, intellectual, irreverent, political leanings, background music, et cetera. Maybe you like slow long-form woodworking content but like fast-paced travel guides. Maybe you hate background music except when it's in skateboarding videos. To determine this requires an incredible amount of "questioning" of the user.
Now, of course, an algorithm that updates once daily can also make inferences about your interests and preferences. It can certainly learn, with enough time, what you are into and how you like to consume it. But the key thing is that these inferences only enable _predetermined_ changes. Imagine you are a human showing someone TikToks. Imagine that you can ask them any questions about their preferences right as they watch a video. You may not ask a question after every video, but you will ask countless questions over the hours of scrolling that day, and you will get good data. Now imagine a new restriction: you must decide your questions once a day in advance. You will manage far fewer questions; and to follow up on them you must wait yet another day.
Now, why do I partly agree? Well, I don't think speed is everything; I think TikTok has another sort of je ne sais quoi to it. I think it has a unique culture and community. It has a better UI and better features than Instagram. It has a young and cool reputation, far from the Millennial taint of Instagram or Facebook. And I suspect that they are good at identifying _who_ you are and acting on that information. But in my eyes, the speed could very well be the most important part of the puzzle.