The Congress is an obstacle to those who want to build an alternative. A large mainstream party acts like a magnet that catches a lot of energy around it. So, even when the Congress is unable to defeat the BJP, it ends up diverting and diffusing a lot of the energy that gets drawn to it.
This agitation is not against English but against the dominance of English. It is against the presumption that the national talent resides within the tiny pool of English speakers.