。
Reviews of the play were generally favorable.
Literal
Play [attributive-の] review [topic-は] overall good-review was-[copula-past-だった].
おしなべて ('overall, generally, across the board') is a literary adverb you'll meet in book reviews and essays — more refined than 全体的に. 好評 ('good review, favorable reception') contrasts with 不評 ('bad review'); the pair often appears in entertainment, dining, and product reviews. Simple theater-review sentence.