The original statement assumes that someone does not know nothing and has to start from scratch.
In any way I am all in for the type of developers that know how to screw size 8 bolt into size 8 nut and the rest be damned. It keeps some healthy niche and remuneration for little more versatile types.
And since you have to know the web stack to exist at all on browsers that box is checked for basically everyone. Break the dominance on the DOM and JS in browsers and you open the door to better cross-platform toolkits.
It is a lot faster if you already know web tech stack, and you would have to learn Lazarus/pascal