I've been trying to find a quote (from Fellini, I believe) but I can't. It was basically that if you examine the whole body of work of any great artist, you will soon discover that that artist is obsessed with something. It may be an idea, or an ideal, or a problem that needs solving, or an image, another artist, etc...
I find this so be true. If it is in fact true, then what is Philip Glass obsessed with?
He is not obsessed with "repetition". He is obsessed with a handful of rhythmic patterns and arpeggios, and much of his post-EOTB music is a frantic re-working of those same patterns and arpeggios into as many different configurations as possible. This listener finds the results extraordinarily moving and fascinating to indulge in.
Some listeners just can't be pleased. The same listener might complain that Glass is too repetitious while Webern or Schoenberg isn't repetitious enough. Glass uses repetition as a musical tool, same as Webern uses a tone-row. And the repetition of Glass is deceptive. It only seems repetitious, but if by "repetition" you mean "the same thing over and over and over", then I am afraid you are mistaken. If you listen closely to any section of EOTB or Koyaanisqatsi you will discover that with almost every so-called "repetition" some sort of change has occurred. The drama and intensity in the music comes largely from the fact that the development occurs over a longer period of time than you may be used to.
To call Philip Glass' music "bad" is to be a bad listener, I think. I may not like Aaron Copland's music very much, but I had no choice to admit that he was certainly gifted and brilliant and he certainly knew what he was doing. I could say the same for the poetry of Sylvia Plath. I do not enjoy reading her work, but I would never be foolish enough to call her a "bad" poet.
Glass is often compared and contrasted with Reich. What Glass has that Reich does not have is a thorough training in the Western classical tradition. He understands harmony and form in a way that Reich does not. Glass has a historic grasp of the tradition he is a part of, and Reich does not. Once again, this does not make Reich "bad". But to call Glass "bad" is to overlook how great his sense of melody is, how lush his harmonies and orchestrations can be, and how unique his music is among music.
I personally find that Einstein On The Beach is when he got good, and he has been great ever since.