The fact that the Messiah has not come means the claim to be the Messiah is not worth the time or the effort of thinking about it.
And you're wrong that Jesus was the only person for whom this was claimed.
Here's a list of people who either declared themselves the messiah or other people declared them the messiah...
- Judas son of Hezekiah (Ezekias) (c. 4 BCE)
- Simon son of Joseph (c. 4 BCE) a former slave of Herod the Great who rebelled. The messiah of Gabriel's Revelation.
- Athronges (c. 4-2? BCE)
- Jesus of Nazareth (ca. 4 BC - AD 30-?), in the Roman province of Iudaea. Jews who believed him to be the Messiah were the first Christians.
- Theudas (44-46)
- Menahem ben Judah partook in a revolt against Agrippa II in Judea
- Simon bar Kokhba (died c. 135), defeated in the Bar Kokhba revolt
- Moses of Crete (5th century)
- Isḥaḳ ben Ya'ḳub Obadiah Abu 'Isa al-Isfahani of Ispahan lived in Persia during the reign of the Umayyad Caliph 'Abd al-Malik ibn Marwan (684-705).
- Yudghan, lived and taught in Persia in the early eighth century disciple of Isḥaḳ ben Ya'ḳub Obadiah Abu 'Isa al-Isfahani of Ispahan
- Serene (Sherini, Sheria, Serenus, Zonoria, Saüra) (c. 720)
- David Alroy or Alrui (c. 1160)
- Abraham Abulafia (b. 1240)
- Nissim ben Abraham (c. 1295) active in Avila.
- Moses Botarel of Cisneros (c. 1413)
- Asher Kay (1502) a German near Venice.
- David Reubeni (early sixteenth century).
- Solomon Molcho (early sixteenth century).
- Sabbatai Zevi (alternative spellings: Shabbetai, Sabbetai, Shabbesai; Zvi, Tzvi) (1626-1676)
- Barukhia Russo (Osman Baba), successor of Sabbatai Zevi.
- Miguel (Abraham) Cardoso (b. 1630)
- Mordecai Mokiakh ("the Rebuker" of Eisenstadt (active 1678-1683)
- Jacob Querido (d. 1690), said to be the reincarnation of Shabbetai Zevi.
- Löbele Prossnitz (Joseph ben Jacob), early eighteenth century
- Jacob Joseph Frank (1726-1791), founder of the Frankist movement.
- Shukr Kuhayl I, 19th-century Yemenite pseudo-messiah
- Rabbi Nachman of Breslov (Hebrew: נחמן מברסלב‎, Nachman from Uman (April 4, 1772 October 16, 1810), was the founder of the Breslov Hasidic dynasty.
- Judah ben Shalom (Shukr Kuhayl II), 19th-century Yemenite pseudo-messiah
- Menachem Mendel Schneerson; a 20th century Rabbi and charismatic leader who is believed to be the Messiah by many of his adherents.
Of course, by the time these people died, it became perfectly clear that they were not the Messiah, although for some of them, they probably could have been. (Jesus is not one of them that probably could have been, from what I've read about him.)
Claiming to be the Messiah does NOT make anyone worth of my time as a Jew, because the simple fact remains that we are not in the messianic age.
There is not world peace, there is no Temple in Jerusalem, all the children of Israel are not living in Israel.
The notion that the Messiah had come already is at best a joke, and at worst an attempt to lead Jews away from the Torah by accepting things that were not told to them by the prophets. The acceptance of the idea that the messiah has already come is equal to the rejection of prophecy... which is to say, the rejection of God's word, which amounts to a rejection of God.