Zerodha may well be the biggest but their platforms are full of glitches. There was a time when it was bug free but now it definitely doesn’t do proper maths. Their back office platform shows inccurate numbers since last 1 year for a minimum. I have highlighted this multiple times to their support team and they keep saying they are moving back office platform to new one called CRUX soon. Also as they have grown in number their support has consistently deteriorated. I have been with Zerodha for quite a few years now and can say that support quality now is nothing short of frustrating.
While I completely agree that discount brokerage is the way forward it may not be wise to go with largest ones since they may not be able to scale appropriately. Perhaps retail should consider budding/newer discount brokerage services instead. At least till the time newer firms are hungry and willing to provide good support and then once they reach a certain number re-evaluate if success has gone to their head and if it’s time to move on