yeah, in theory, that's how national politics work too in allegedly democratic countries, based on consensus, how's that working for you?

more to the point, as stated on steem.center wiki

"A hard fork is a change to a cryptocurrency protocol that makes previously invalid blocks/transactions valid, and therefore requires all users / software to upgrade.[1] It could be any alteration to a coin which changes the block structure (including block hash), difficulty rules, or increases the set of valid transactions. You can think of a hard fork as a change of rules.

Free and open source software may be legally forked without prior approval of those currently developing, managing, or distributing the software. In free software, forks often result from a schism over different goals or personality clashes. In a fork, both parties assume nearly identical code bases, but typically only the larger group, or whoever controls the Web site, will retain the full original name and the associated user community.[2]

The Steem Blockchain has an innovative Witness-based system that allows improvements to be made to the protocol more rapidly than other blockchain protocols. All that is necessary for a Steem hardfork is for the top 20 witnesses, who are chosen by the users, to adopt the changes based on their assessment that the code is bug-free and does not pose a threat to the security of the blockchain." - https://www.steem.center/index.php?title=Hard_Fork

So yeah, your concept is correct, but actually getting 20 like minded witnesses and getting them all to agree to a specific hardfork, which first must be coded, and proposed, is like, well, good luck. It takes a DRASTIC hardfork to get that kind of buy in and even then, there is lots of angst. We have had 19 hardforks so far, and each time, it causes much adjustment around here. For better or for worse. But your ideal of getting all altruistic witnesses into the top 20, is effectively about as possible as changing a nation's politics without guns.