R’ Moshe Sternbuch (Teshuvos V’Hanhogas 2:649) also deals with the above. Firstly, he says, the above only applies to a chasunah seudah of a talmid chocham to the daugther of a talmud chocham, and nowadays no one is really considered to be a talmid chocham (the Gemara mention this many times).
Then he adds, one only gets punished for not attending if the reason he doesn’t attend is because he holds it’s below his dignity to attend such a lowly seudah, if, however, the reason he doesn’t attend is because he is busy learning, or he is busy with some other matter then he doesn’t get punished for not attending.
R’ Moshe continues, if one doesn’t attend a chasunah due to the mere fact that it takes a long time, and not because he feels it’s below his dignity, there is nothing wrong with not attending. By a bris seudah, however, which is much shorter, one should make more of an effort to go.
He mentions that he heard from R’ Meir Chodosh, that that which Chazal say about going to a chasunah seudah only applies to the actual seudah, it wasn’t said about the journeys and time wasted before one arrives. Therefore, if one has to waste lots of his time in order to get there, it’s better to learn than to go to the chasunah. (See also Teshuvos V’Hanhogas 3:401)
