Any text longer than 2-3 words written in all caps turns into a shouting piece that users have trouble reading and may even lose interest in. Why does this happen?

Many studies have been conducted to explain it. One study suggests that people don't read letter-by-letter but rather recognize ascending and descending words' outlines. All caps doesn't have these variations, making it harder to read longer pieces of writing in all caps.^[1]

No matter which theory you prefer, all caps feel unfamiliar to ordinary people, making text notably hard to digest. Additionally, most screen readers will spell out text in all caps letter by letter, leading to a terrible user experience. It can be okay to use all caps for headlines, subheads, labels, and other short phrases. Captions, however, appear illegible and impose a higher cognitive load.

In turn, in sentence case, letters are more distinctive, and text feels familiar and natural — that's how we have grown up reading, after all.