That would rule out almost all server side templating systems, and most non-JSX client side ones (svelte, vue and angular all involve it to some extent) so I don't think that's quite right.
I think maybe you've misread the author talking about the fact that most server side templating systems are fundamentally fancy ways to concatenate text as meaning writing the literal text concatenation yourself without having a library do it for you?
I think maybe you've misread the author talking about the fact that most server side templating systems are fundamentally fancy ways to concatenate text as meaning writing the literal text concatenation yourself without having a library do it for you?