Why do you think it's a failure? The fact that we don't have any press release explaining that the company is making millions doesn't prove it has failed. Let just says that there are many exchanges out there, and that Gemini isn't different enough from the others, besides its rich backers.
You may also look at BTC as a whole which remains far from its $1,000 record of 2014.
I think it's a huge success. Now if their bitcoin ETF is half as successful...