"What they mean" isn't correct or reasonable and is largely part of the same grumbling groupthink that willfully refuses to come to grips with the realities of the tools they've decided they don't like.
React is not large, is of moderate complexity (most of the complexity of "a React app" lives well outside of React itself), and can be stripped down to a fully static templating language without much effort. As I've linked elsewhere, I turned React into an email templating engine once because I don't like Handlebars; rendering JSX as static, no-JS HTML is a one-liner when you throw it a React component.
React is not large, is of moderate complexity (most of the complexity of "a React app" lives well outside of React itself), and can be stripped down to a fully static templating language without much effort. As I've linked elsewhere, I turned React into an email templating engine once because I don't like Handlebars; rendering JSX as static, no-JS HTML is a one-liner when you throw it a React component.
Using React for a static website is totally fine.
So is not using it.
Being weird about it is not fine.