While maybe slightly curt, I do echo this statement. Nothing on the demo page displays anything you couldn't do with a static page. Using tools devs are familiar with can often be good, but here it's hard to see the benefit.
eh, not necessarily, you could claim using a popular framework has it's benefits. It's easier to transition it to a full app whenever the time comes. The author could've chosen something less hip?, sure, but again React is widely used and it has proven to be useful in many app scenarios.
Why not? It's the most popular UI framework. The second you start building a SAAS product on top of those pages, you're not going to want to be in vanilla land.
Because you want your landing page to load instantly and React or any other JS-generated site just can't compete in loading speed with a static HTML page.
Uhm, probably not the best idea to mix your saas application, with your business website. I would definitely not recommend that.
And i will also echo the other comments, saying that this is definitely overkill. If you're doing a single landing page, jsut go with static html/css. If you need some content management, then either go with a fully fledged CMS or do the hipster thing and compile into static site.
Because you need a bit of CSS knowledge and to know how intersection observers have to be configured and then everything works with few lines of JS and CSS ... it's lightweight and SEO friendly and not bloated as if you use REACT.