It sounds like an excuse, they can do so without India. It doesn't have to be under the BRICS banner.
It is not an excuse. It's a structural flaw of BRICS. Some members are already doing bilateral trades without USD. They just cannot come around to do it collectively as BRICS. Because it apparently requires unanimous support from at least the founding members.
Without a BRICS basket of currencies, smaller economies who lack foreign reserves cannot wean themselves off the USD. Like it or not, the USD is still the most easily convertible currency today. Long story short, without an easily convertible basket of non-USD currencies, there are no true alternative currencies for international trade.
Trade can still happen without the USD, but it'll take some time for smaller economies to build appreciable reserves of the major non-USD currencies like the Yuan or Ruble. It's not an easy decision to make as you can't easily buy Russian oil with Yuan, or easily buy Chinese goods with Ruble. That was why BRICS could have cleared up this mess by creating the basket of currencies. Now the major economies of BRICS have to find a workaround for this.
BRICS doesn't appear to have an expulsion mechanism. So the "I" in BRICS can continue to spoil it forever. It had been a great blunder to conclude that nation into BRICS. But when BRICS was founded in 2009, many of the founding members had underestimated that nation's potential for duplicity and treachery.
