What makes React complex is that your simple example pulls in 100KB of code and entire layers like the virtual DOM which increase the memory and CPU requirements while adding significant new concepts a developer has to learn to be productive.
That’s not to say that there aren’t benefits from that but it’s definitely extra complexity compared to using web standards.
You don’t need to know how JPEG or AVIF work internally to use an <img> tag.
> Meanwhile, there simply aren’t web standards that match React’s capabilities.
This isn't true for much of the web but it’s more deeply missing the point: if you’re building a web app, you need to learn the web APIs because those are what all web apps actually use. Adding intermediaries means that you have more things to learn, troubleshoot, and optimize. React’s value comes from managing the complexity of the code you write, which can be a real benefit for some projects but it doesn’t remove the need for you to know how browsers work.
That’s not to say that there aren’t benefits from that but it’s definitely extra complexity compared to using web standards.