When the DM is largely responsible for giving the party magic items (as is the case with 5e), it is absolutely the fault of the DM for throwing something against them that multiple members of the party are fully useless against, especially at a low level.
“hey, this world has magic in it, let’s all decide to go in fully unprepared to deal with it!” is not the fault of the DM
When the DM is largely responsible for giving the party magic items (as is the case with 5e), it is absolutely the fault of the DM for throwing something against them that multiple members of the party are fully useless against, especially at a low level.