Question:

What did the sages mean with their prediction that in the era before Moshiach, “The face of the generation will be like the face of a dog”?  

Answer:

The eminent Rabbi Yisrael Salanter of blessed memory once explained this teaching as follows: 

A dog by nature runs ahead of its master, always turning around to see where he is heading; whatever that direction may be, the dog arrives there first.

Now in common Hebrew and Yiddish parlance, the phrase pnei hador (here translated as “the face of the generation”) often signifies those who are [supposed to be] the leaders of the generation.  In our days, however, on the eve of the Redemption, these ostensible leaders merely look around to see where their congregants would like to head, and they run there first…

This quotation may also be understood as alluding to a dog’s perpetual appetite.

 On the eve of the coming of Moshiach, the entire generation will be hungry for the word of G-d, as is written:  “Behold, days are coming,’ says the L-rd G-d, ‘when I will send a famine in the land.  Not a famine for bread, nor a thirst for water, but for hearing the word of G-d.’”  Every man in that day will be as hungry as a dog, in the spirit of the verse, “The dogs… are never sated.”  Whatever they are given is never enough; they are forever demanding more.  In the generation before Moshiach we will experience an insatiable appetite for spirituality that will be sated only with the revelations of the Messianic era.

(Sotah 9:15. Letters of the Previous Rebbe, Vol. VII, p. 59. Amos, 8:11. Isaiah 46:11. Likutei Sichos Vol IX, p. 105. From Exile to Redemption, pp. 65-6)