all hat and no cowboy

US idiomatic not-comparable

(US, idiomatic) Full of big talk but lacking action, power, or substance; pretentious.

Japanese Meaning

口先だけで実際の行動や実力が伴わず、見せかけだけの派手さがある / 大言壮語だが結果や中身に欠ける、見せかけばかりの / 表面上は立派に見えるが、実際の力や実行力が乏しい

The campaign manager is all hat and no cowboy, promising reforms but delivering none.

その選挙運動のマネージャーは口先だけで行動が伴わず、改革を約束するが何も実行しない。

Sense（1）

(US, idiomatic) Full of big talk but lacking action, power, or substance; pretentious.

Don't waste your time with him - he's all hat and no cowboy.