Is saying "There is no longer any blessing in these days" considered a word of disbelief (kufr) that necessitates reaffirming the Two Testimonies (Shahadatayn), or is it a bad word that requires seeking forgiveness (istighfar) and repentance (tawbah)?

The statement mentioned is not considered disbelief because the loss of blessing can occur due to sins. As Ibn al-Qayyim mentioned, sins obliterate the blessing of one's life, sustenance, knowledge, deeds, and obedience, and they remove blessing from both religious and worldly matters. Quranic verses and prophetic traditions have indicated this, for Allah opens blessings from the heavens for those who believe and are righteous, and He deprives a servant of sustenance due to a sin. What is with Allah cannot be attained except through obedience to Him. No one is judged to have apostatized unless they have truly committed an act that necessitates it, along with the establishment of proof, the fulfillment of conditions, and the absence of impediments.