- Create a proposal that has no significant opposition. A proposal has significant opposition if it is strongly opposed by any of: one Bitcoin Core committer, one large exchange or company (Coinbase, etc.), a few generally-recognized Bitcoin experts, several smaller but still economically-important companies, or a large group of ordinary users who have reasonable arguments and are willing and able to exert some real economic force. (The underlined groups are the ones with clearly-significant opposition as I currently see things.) This means that it's very difficult to do controversial hardforks. That's the point. You need to get consensus -- that is, make a hardfork non-controversial -- in order to do it.
Yes, absolutely, I agree completely. if we want a truly consensus and decentralized Bitcoin, we must give lone third parties the absolute power to veto any and all changes. Yes! This is the answer Bitcoin needs! /s
By this logic, Blockstream could maintain a 1MB block limit and force Bitcoin users worldwide to use their service.
Actually they can't. Blockstream doesn't even offer a service yet, so they aren't considered a large company or exchange. They would count as a smaller but still economically important company. If they were the only ones who opposed a block size increase, then they do not count as several companies (just one company) so they would be disregarded provided that everyone else in that list agrees with the change.