noun which may take the genitive case particle 'no', noun
all show and no substance; not as good as it looks
Describes something that appears impressive or strong at first glance but turns out to be weak, worthless, or disappointing upon closer inspection. Often used for people, products, or claims.
That player was all show and no substance; he didn't perform at all in the match.
This software is not as good as it looks; most of its features are unusable.