A month is enough for a technology or two. But we are talking about developers that are supposed to use like twenty different technologies at the same time, and

A month is enough for a technology or two. But we are talking about developers that are supposed to use like twenty different technologies at the same time, and maybe need to learn five or seven of them. And often the reason a company wants one person to use twenty different technologies is that they can hire as few people as possible. Which means, there often isn't a more experienced colleague at the workplace to learn from. And no, the company is not going to pay you a training either.