> what you should expect the average developer to know This sounds like unnecessary gatekeeping. By whose standards? Most of the web runs on JavaScript and PHP

> what you should expect the average developer to know This sounds like unnecessary gatekeeping. By whose standards? Most of the web runs on JavaScript and PHP. With TypeScript the frontend is steadily moving towards more "type safety" (an ambiguous term). But the point is that most of the useful things on the web have been built using languages that take the opposite approach. And there is a good argument to be made that a dead simple learning curve (without having to learn about types for example) is how we ended up with so many webapps so quickly. Much of the early web was built by amateurs.