1. While younger consumers know about Apple (and know that it is a "superior" brand), the native Apple ecosystem has little meaning for Indian consumers. They are not on iTunes or iMessages or FaceTime. They don't have a cultural relationship with a Mac (or an iPod).
2. Google/Android got there first (2008). Xiaomi, Samsung have benefited from it.
3. The network (and its accompanying data plan) is the differentiator, not the hardware. Look how Reliance Jio exploded.
4. The wealthy/upwardly mobile love their iPhones.
5. There's a HUGE grey market for phones in India. There's also a big repair market. Both these factors probably affect new handset sales?