not all it's cracked up to be

not all/everything sth cracked up to be (not as good as something is said to be; not as good as people say.) — не оправдывать ожиданий; не соответствовать тому, что говорят; не соотвествовать своей репутации

Example 1: This isn’t a very good car. It’s not all it’s cracked up to be.

Example 2: Is Moscow all it’s cracked up to be?

Example 3: This hotel isn’t what it’s cracked up to be.

Example 4: The only reason to see the film is for the special effects, and even they're not all they're cracked up to be. It has as much intelligence as boiled cabbage.

Lookyhere, Tom, being rich ain't what it's cracked up to be. It's just worry and worry, and sweat and sweat, and a-wishing you was dead all the time. (The Adventures of Tom Sawyer: Huck's Monologue)

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In the 15th century, the verb crack meant to boast or praise something. If something was therefore cracked up, it was said to be good or worthwhile. Something that was not all it was cracked up to be meant literally not as good as what people boasted it to be