Apart from babbling about the necessity of BIP 101, what they can do against the will of the majority? If they can't persuade the miners they can keep talking what they want and as much they want but that's not going to move their case anywhere.
And why should only one company be deciding bitcoin development, every player in the business should have an input.
Coinbase business is injured because all of these delays in transaction confirmation, and this is happening because Blockstream hijacked bitcoin development and are now creating a necessity for their business by not increasing block size.
And you're right there's very little they can do, íf a company wants to have anything to say about the bitcoin development it has to buy all the developers, touché Blockstream.