Customs vs. Belief

peace,
Is there an obligation to continue family/ethnic customs even if one believes they should be changed?
The specific context is mourning customs related to the destruction that were expanded over the generations. If we believe that with the return to Zion and the establishment of the state, it is appropriate to reduce mourning, since the exile is over and all that is missing is the building of the Temple (perhaps the Messiah), and there is a good reason to continue mourning while ignoring the great good that God has done for us in recent generations, is it possible to abolish some of the customs and perhaps return to the law of the Gemara (for example, like the Yemenites)?
Thank you very much.