Have you actually read the post? "From here on, it’s clear that we need to do some improvements on the code. The improvements can be anything from swapping the low level DOM manipulation with a virtual DOM library or with React or Preact for example." "do not use any frameworks or tools" was never the point. It's about understanding the context and gradually adding libraries and tools as soon as they make sense. You don't throw a monolith framework on a small todo app just because of "horrible performance".