不瘟不火
bù​wēn​bù​huǒ

neither dull nor overacted

不瘟不火 bù​wēn​bù​huǒ
neither dull nor overacted
(of an artistic performance) just right; neither dull and boring nor excessive and over-the-top
lukewarm; mediocre
(of business, popularity, or sales) neither hot nor cold; lacking enthusiasm or major success; mediocre; this modern usage is an extension or misuse of the original theatrical meaning