A lot of the other Chinese apps were clones. TikTock was a novel improvement to the crap of Twitter and Facebook, etc. And it's algo is(was?) very "good"
That being said, I would take that claim with a big grain of salt, for multiple reasons. First you need to look at the relevant generation where tiktok is strong, whether youtube can break that monopoly. Also, it's fairly easy to make existing youtube users "try out" shorts via an in app pop up, and then mark that down as successful use of the feature. If your app has enough users, you can reach relevant usage counts easily, even though none of the users are there for the shorts feature only.
Also, what matters with social apps like these is also not just the content consumption but whether friend groups etc. are communicating on that app or another one. This has extremely strong network effects that are hard to break.
[0]: https://www.investors.com/news/technology/google-stock-rises...
But it wasn't built to appeal me (or you), but other parts of the population, people who prefer tiktok like experiences.
For me personally, the reason to use shorts every now and then is because tiktok is authwalled while shorts is not. But I don't know what other users of shorts would say why they prefer it.
Just trying to recreate some of the UI aspects of it is just cargo culting.
YouTube could be just as good, even without shorts, if it actually gave people what they want instead of what makes YT the absolute maximum amount of money over.