、。
You're saying I'm clueless about trends, aren't you.
Literal
I [topic-は] trend [to-に] insensitive [is-だ]-[colloquial-quotative-って], you [topic-は] saying-[state-ている] [but-けど]-[agreement-ね].
って is the colloquial quotative particle (contracted from と). 鈍感 ('insensitive, dull to perception,' literally 'dull sense') is a な-adjective. 言っているけど ('are saying, but...') uses けど for soft concession. 流行 ('fashion trend, fad'). A self-aware response to a friend's teasing criticism.