Is one who truly believed in the message of Prophet Jesus, and was alive during the time of Prophet Muhammad but did not believe in the Prophet's message, considered a disbeliever?

The term "disbeliever" (kafir) is applied to anyone who has not believed in the message of our Prophet Muhammad, peace and blessings be upon him, even if they believed in prophets before him. Christians who have not believed in Muhammad, peace and blessings be upon him, or have associated partners with Allah, or have denied the prophethood of any prophet, are considered disbelievers according to the texts of the Quran, the Sunnah, and scholarly consensus. Therefore, whoever embraces a religion other than Islam, their religion will not be accepted from them, and they will be among the losers in the Hereafter, as Allah Almighty says: "And whoever desires a religion other than Islam, it will never be accepted from him, and in the Hereafter he will be among the losers" (Quran 3:85). And Allah Almighty's statement: "Those are the disbelievers, truly" (Quran 4:151) confirms their disbelief.