I think this is both right and wrong. Granting Sturgeon's law, most code is bad and hard to read and type annotations will usually help. On the other hand, in code that is very well written, type annotations are largely redundant visual clutter that do not improve the readability.

I'd say that for most people, use annotations most of the time is good advice, but there are exceptions and people should refrain from casting judgment on other's work due to a dogmatic instance on others using their preferred style.