The biggest downside of knockout is that it parses the template from the dom, and the template is rendered as dom until first execution. Then that it eval it's bindings. I suppose tko should help with those issues but seems kinda dead.
Knockout reactivity primitives are also a lot more naive then modern signals implementations.
Compare: "import a specific lightweight library and wire together as needed" vs "write the whole app in terms of a bloated framework".
I've been out of the frontend game for a while, but what does react give you that knockout and maybe some url management logic do not?
I guess components are supposed to standardize modularity, so you can easily import some random widget?