What is the reason for practicing Jewish traditions, and which traditions?
If you mean for instance in a mixed marriage between a Jew and a Catholic, they might observe both Hannukuh and Christmas customs for the sake of the children, or celebrate Passover, fine.
If you mean a Christian convert from Judaism who retains some of the cultural and religious practices of his childhood, such as the dietary rules he has grown up with, fine.
If you mean a Christian with no particular Jewish background, who decides to dress, pray, follow kosher laws, imitate a seder or hold himself out as Jewish, that to me could easily become insulting to Jews in his vicinity and some Jews have commented they consider such things as “aping” their religion so should be avoided on that grounds alone.
If you mean adhering to all the laws of Leviticus etc. as some kind of statement that they are still commanded, that is wrong for Christians, we have the testimony in Acts for that. Still further to insist Christian convert adhere to those laws is contrary to the Faith as well. If the practices are based on imperfect understanding of the Christian faith the wrong multiplies.
The governing principle here above all should be charity to our Jewish elder brothers in faith.
There is no temple so that does not arise and at least sounds mean spirited, don’t know how it was meant.
Messianic Jews, as an organized sect, misstate so much of Catholic teaching they are not good examples.