Indeed, It is a Shaktipeetha.
There exists a widespread misconception among many people regarding Kalighata Kali Temple, namely the belief that it does not constitute Shaktipeetha. However, such assumptions stand in direct contradiction to the broader and numerous sources. In reality, Kalighat has long been acknowledged as a Shaktipitha and occupies a far more prominent and celebrated position.
नकुलीशः कालीपीठे दक्षपादाङ्गुली च मे । सर्वसिद्धिकरी देवी कालिका तत्र देवता ॥
At Kaalipeetha, The Right Toe Fingers of Bhagavati Dakshayani fell, Bhagavan Shiv is there as Nakulisha Bhairava, While Bhagavati there is as Kalika, the bestower of Siddhis.
—Peethachudamani & Pranatoshini Tantra
कालीघट्टं गुप्ततीर्थं सिद्धाख्यं सर्वमोहनम्
In Kaliyuga, Kaalighaata is hidden tirtha, Known as Siddhakshetra.
कालीघट्टे महापीठे काली कालात्मिका तथा
At Kalighata, The great Shaktiptha, is Bhagavati Kali, Who is Antaryamini of Bhagavan Mahakala.
—Brrihannila Tantra
Another Part of Pranatoshini mentions Daivatya of Peetha as Bhagavati Jayadurga and Brrihannila calls her as Bhagavati Guhyakali. So It indeed is a Shaktiptha.
कालीघट्टे कलौ काले किल्विषौघनिकृन्तनी । सपत्नीविभवं दृष्ट्वा गङ्गाऽभून्मलिना कृशा ॥
In this age of Kaliyuga, Devi Ganga, destroyer of all sins, came to Kalighat and, seeing the splendor of her co-wife i.e. Bhagavati Kali, Ganga grew wan and thin with jealous sorrow.