A centralized system is any system which at any point power can be consolidated and effectively brought to bear to coerce, control or otherwise forcibly influence an otherwise autonomous actor.
Some would say that "direct democracy" is anarchy. This is patently false. In fact, true democracy is the opposite of anarchy. In a true democracy, the law may constantly change at the whim of the masses, but the will of the masses is the supreme law.
In direct democracy the majority still has full coercive control of the minority - even though though the power is diffused thoughout the electorate. In this way, a pure the power of a democracy is just as centralized as a dictatorship, even though the authority to exercise that power is diffused throughout the electorate. That authority becomes consolidated at the ballot box and is centralized into power and control through whatever mechanism is put in place to enforce the will of the majority over the minority of dissenters. This enforcement is usually at least implicitly by threat of lethal force if the minority does not comply.
So, if 50.1% of the population of a pure democracy decided that 49.9% should be rounded up and put in gas chambers or brought before a firing squad, that's what would happen. Likewise, if 50.1% were persuaded and manipulated to grant the title of "dictator for life" to an egomaniacal madman, that's what would happen. Bye bye democracy.
Direct democracy is just a different form of tyranny - it is tyranny of the majority over the minority.
So, the thing to remember is that in a "direct democracy, the fractional authority of the individual voter gets combined. And when they have 50.000001%, they have the power to enact their will in some centralized manner. It is inherently a centralized system.
A fully decentralized system is one where, except for the voluntary interactions of autonomous entities there is absolutely no means of coercive or forcible control of one autonomous entity over another autonomous entity. The radical Libertarian party of the U.S. tends toward this direction. Though I suspect that they would agree that there does need to be a mechanism to enforce valid and binding agreements between autonomous entities which would be 'government.' (I am not a radical Libertarian, btw.)
It is the possibility of coersion and control that is the mark of centralization - no matter how "diffuse" the power to exert it is. If authority can be consolidated and power brought to bear over otherwise autonomous entities, the system is centralized.
In OpenSource where the code is freely available and can be edited and redistributed by anyone, it really is only the free and voluntary interactions that hold sway. If you want something changed you are free to do so and redistribute your code. If other autonomous actors see the benefit, they will adopt your changes. If they don't, well, there it is.
Of course, aware of this, it is beneficial for maintainers to be aware and sensitive to the needs of those using the software. But the "coercive force" brought to bear when that doesn't happen is often a fork or an all out abandonment of the project if the maintainers remain tone deaf and those who have adopted the software lose confidence.
I say all of this to avoid the possibility that some will confuse the ability to "have a say" in what happens (for example, by enacting some form of democratic reforms) with a truly "decentralized" system.
A democratic system is just as antithetical to the aims and princies of Free/Libre software created in a distributed environment no less than the tyrrany of closed source systems. It's just the opposite side of the same coin.
The customer service industry has rightly abandoned the motto, "The customer is always right.". Because, objectively, it is a false statement.
Elsewhere, I have outlined ways for individuals or groups within an opensource ecosystem to "have a say" in the project that respects the decentralized nature of OpenSource/Free/Libre software and made some very specific suggestions with regard to Hubzilla - a robust and mature decentralized and fully distributed identity, access control and message passing platform that has the potential to disrupt the current environment of centralized service providers of Social Media services and many other centralized systems.
A truly decentralized system puts the power of decision making along with the right and responsibility to be the actual agent of change in the hands of each autonomous entity either working alone or in voluntary association with others. This is the heart and soul of OpenSource "Free/Libre" software. It is also the heart and soul of Hubzilla as I have come to understand it's background and the intentions of those who have brought it to where it is today.
If you want to try out Hubzilla, gather a few friends and visit https://usezot.com
for test-drive accounts and play around. The software is continuing to evolve and there are other hubs available ( https://hub.webgoeslocal.net/pubsites
Once you understand the possibilities of decentralization, you'll never want to go back to centralized systems --- even in software development!