They have advertisements in a lot of places, but Mumbai has mostly been a place where big ISP players divide places and have their own small monopoly and the small ISPs squeeze in through over a very small proportion. My complex is approx. a 1x0.5km rectangle and 70-80% of customers do and prefer using JioFiber here, thanks to that you won't see any JioFiber ads and they are slowly capturing even more seeing how these blue T-shirt jio fiber guys are always busy carrying around equipment.
TBH, the biggest attraction for customers to JioFiber would be the inclusion of STB + OTT + Broadband combo, all at a good price.
Interestingly the high-speed plans for a low price have never been an attraction for me, I'd rather pay more if the connection is actually good even if it's slower than the competition. I was paying ~6K for 6 months on I-ON and they only gave me an 80Mbps connection.