Concept album ? Metallica don't do such things. They are for bands like Pink Floyd and Dream Theater.
Lyrics suck and vocals are not good ? You must be out of your mind. This album has some of the deepest metallica vocals I have ever seen.
And yeah, rock in India is NOT limited to these bands. Its just that these are much better than common BS I hear. I love thrash metal in the style played by Metallica, Megadeth and Anthrax, but these modern thrash bands have hardly any music. All of them just over-use blast beats, double bass, roaring vocals which make no sense, gory themes and next to zero melody. Music is eternal. Look at indian classical music. Its been living for thousands of years. Similarly classical metal would also live on for eternity. Bands may die, but their music lives on forever, and people always exist to carry forward the legacy.