。
You really are a picky eater, aren't you.
Literal
Truly likes-dislikes [subject-が] is-intense [explanation-んだから].
好き嫌い is a compound noun (likes + dislikes) commonly referring to picky eating preferences, and 激しい ('intense / fierce') is a strong descriptor here meaning 'very.' The sentence-final ~んだから is the colloquial ~のだから — an explanatory framing that asserts the observation as self-evident or pointed, often with a tone of resigned complaint. Subject is omitted but clearly the addressee.