Hair is a historic relic, it is an example of the alternative theatre movement that arose amidst the generational rift of the late 60's, and is primarily a war (read "draft") protest piece that has little resonance today due to a lack of a draft, in spite of our current involvement in wars abroad. As is all too typically the case with professional productions which are weak on relevant material, the burden falls on the shoulders of the actors to punch it up and try to make it entertaining while uttering words that fall flat. This leads to exaggerated, "sell it to the back row" acting that quickly grows tiring and even annoying to watch. Being alternative theatre, it has virtually no plot, but is mostly a strung together set of musical numbers each making a little point about the times it seeks to document. The only thin connecting line of story is one character having to come to terms with being drafted and having to leave the hippy, bohemian life he's come to love. It's not enough to carry the show.
All that could be forgiven if there had been great music. There's little music of note in this show. The perhaps three or four songs melodious enough to be enjoyable are already known outside of this show, but the rest of the music rarely pulls together enough of a tune to tap a toe to. Further, given the "let it all hang out" theme of both the production and the spirit of the original composition, the music never rises to a level of sophistication to dazzle with complexity and evocative arrangement. In this particular production, matters were not helped much by a sound system that muffled things to the point that only rarely made lyrics audible.
In other words, it was a dumb show.