Wikipedia describes the reaction as thus:
What most offended Ibsen's contemporaries was what they regarded as its shocking indecency, its more than frank treatment of a forbidden topic. An English critic was later to describe it as "a dirty deed done in public," and to many it must have seemed simply shocking rather than in any profound intellectual sense revolutionary.
At the time, the mere mention of venereal disease was scandalous, but to show that even a person who followed society's ideals of morality had no protection against it was beyond the pale. Mrs. Alving's is not the noble life which Victorians believed would result from fulfilling one's duty rather than following one's desires. Those idealized beliefs are only the "ghosts" of the past, haunting the present.
The production of Ghosts scandalised Norwegian society of the day and Ibsen was strongly criticised.
But is the play relevant today?
Now that we can put nudity and other obscene acts onstage, does the question of the play really matter? Sure there are things that our society finds taboo that perhaps should not be, but there are other plays that handle such topics that are much more accessible. We cannot even identify with this play any more.
However, doesn't this give us something wonderful to aspire to? To write a play that is so relevant and so unsettling that it prompts actual change, isn't that something that our theatre could need right now. August: Osage County received so much attention this year because it is absolutely relevant in the here and now. It may not be enough to cause riots in the aisles, but it is important and people are responding. America needs more plays that have such an effect, create discussion and awareness, and promote change.