Why is that people like Robert Vadra, Priyanka or whoever gets to speak with freedom on any issue related to their party when they have never held any political office? Perhaps American-style party primaries can help check nepotism in Indian political parties. Writing on the topic, WSJ writes this:

No primary process chooses the leader of any of India’s major national or state parties. No leader has emerged in any of the parties with the ability to mobilize the cadre and its members around a new philosophy or even an idea. No major policy has really surfaced as an aggregation of deliberations with party members, activists and supporters. No dissident in a political party in India ever gets to test the popularity of his dissent amongst the party’s larger membership. Amidst a web of district, state and national committees and councils, all major parties have structures that give the semblance of a rigorous, ground-up democracy but are nothing more than a charade to perpetuate incumbents.

Primaries have their challenges too, but democracy is a balancing act:

...the primary processes that regularly churn out compelling leaders as well as bold proposals (and sometimes, if only temporarily, many cockamamie economic and social ideas too, although more often than not, the popular process of the primaries undermines their legitimacy and therefore their presence on a national platform).