Expresses the idea that 'only/exclusively Noun' or 'nothing but Noun'.
Verb-casual + のは Noun + ぐらいのものだ, い-Adjective + のは Noun + ぐらいのものだ,な-Adjective + のは Noun + ぐらいのものだ, Noun + のは Noun + ぐらいのものだ
Long explanation:
The ~のは Noun ぐらいのものだ grammar point is used to express the idea that something is 'only/exclusively Noun' or 'nothing but Noun'. It's used when the speaker wants to express that something is the only thing or point about a certain situation or event. It expresses the speaker’s strong feeling towards a topic or a situation.