Why do so many Jews hate messianic Jews? Or say that their beliefs 'aren't compatible' with Judaism? Isn't Judaism a religion/culture/belief system that has evolved throughout the centuries to adapt (if that's even the right word) to the different questions, views, beliefs or even identities we as humans have? So what makes messianic Jews 'fake Jews' (a term I've literally heard)? Hopefully you don't mind the question im a gentile who follows a lot of Jews and I've just always been curious
Messianic Judaism didn’t emerge organically from Judaism like Chasidism or Reform or Conservative Judaism. It was created by Christians to mimic Judaism in order to “trick” Jews into practicing a Judaized version of Christianity. That alone makes it not a legitimate form of Judaism.
Messianic Judaism appropriates many practices from Rabbinic Judaism which was explicity rejected by Christianity. Jesus never practiced this form of Judaism because the Beit Hamikdash still existed during his lifetime. It doesn’t celebrate what Jesus did during his lifetime, it appropriates what other Jews did after the Romans (who killed Jesus) destroyed our Holy Temple and had to recreate our own form of Judaism in the ashes of Judaea.
So, essentially, Messianic Judaism is both cultural appropriation and an attempt to convert Jews through deceit. It is not recognized by any extant Jewish movement and its adherents do not practice Judaism, even those few who are ethnically Jewish.