They were extremely useful before browsers had certain features, like web components of the Proxy api mentioned in the article.
Today the argument is usually based on highly complex apps, think complex dashboards accessible behind a login or browser-based apps for recording a podcast. Those are reasonable uses for client-side frameworks - the problem is they are often used for much more basic sites that just need a mobile menu, accordion component, or a dialog modal. All of these can either use entirely browser native HTML/CSS or easily built in JS without any dependencies.
Today the argument is usually based on highly complex apps, think complex dashboards accessible behind a login or browser-based apps for recording a podcast. Those are reasonable uses for client-side frameworks - the problem is they are often used for much more basic sites that just need a mobile menu, accordion component, or a dialog modal. All of these can either use entirely browser native HTML/CSS or easily built in JS without any dependencies.