Rav Elyashiv ztz’l” spoke very harshly against today’s sheitels.
These are the words of the Rav translated into English:
“Even though there’s a dispute among the Poskim whether it’s mutar or ossur to wear a sheitel, if they walk as if their hair is revealed, the way those that are not covering their hair walk, they are violating an issur gamur, it’s mamish, it’s emes like ervah. (the term used in gemara to describe parts of the body that must be covered according to halacha)
The issur is as follows: If they walk with a sheitel like the times 100 years ago, then of course this is allowed, even a drop nicer. But, it should not be the way they walk today. All those that walk today, it looks like hair for sure and this is definitely assur, this nobody was mattir.…A woman with the hair of today the way she walks, it’s mamish ervah, it looks like hair, there is no difference, regarding this there is no heter….”
HaRav Chaim Kanievsky shlita stated “If the sheitel looks like hair, it is the obvious truth that it is definitely forbidden. There is no room for dispute in the matter.” He repeated this several times in his conversation with Harav Avraham Lipshitz shlita. (Adorned with Dignity, page 102)