Democratic rule does not prevent tyranny it is not exempt from injustice and immorally. Review the history of Athens if you want to understand this better.
Even far from it!
There is no way to prevent tyranny in a group of different individuals in my experience. Whatever the group and its members, whatever the system, there will always a time where a large majority will say "we do this" ignoring de facto a minority who will get imposed something they don't want.
Democracy is a beautiful word but hiding a complex submissive/dominant reality. People are uprising when you say that democracy isn't perfect and isn't morally good, that it's just an organization system that has its flaws...
I would say that democracy is a bit better over complete dictatorship but there must be even better forms of organization keeping more freedom directly in the hands of the people.
At the end the day the character of the government is dependent on the character of the people. If a population is greedy, lustful, envious, and slothful they will favor leaders and support causes that pander to these vices. Quality of life and governance in general will worsen and the best a systems of checks and balances can do is slow the decay. Similarly if a population is prudent, just, courageous, and charitable then they will elect leaders and support causes promote these virtues.
The real challenge of improving governance over the long term is how do we improve the moral character and virtue of human beings? This is no small task. Indeed it is the most important aspect of progress. Technological advancement is secondary.
There is where the Atheist go wrong. Their solutions here always fail. They sometimes go totally nuts and assume humans are some kind of perfect creature if only the environment was adjusted. Thus leads them to crazy ideas like communism which if you read the actual ideology might work ok for a population of perfect selfless sinless angels but predictably collapses into contradiction, horror, and tyranny when applied to actual human beings.
Or they go the other way and embrace total relativism. They deny the existence of good and evil altogether everything is just preference. There is no value in anything. Anything socially accepted is "good" anything not is "bad". This leads to a willful self-annihilation as I noted
a few posts back. It also lead many atheist leaders to favor drastic population reductions as a way of maintaining control. They grow fearful of an unruly population and their dependence on an unsustainable debt bubble to keep that population happy thus they start to desire the extermination of said population. This is a time honored strategy of tyrants and well documented. It is even described in the Bible as widespread at the time of Moses birth.
The answer to the challenge of good governance is that every generation must prioritize the moral improvement of each individual citizen. This is the necessary prerequisite to ensure future generations will be better off then current generations. God is necessary to this process for without God we are lost in a sea of moral relativism. Without God we can't even define objective good and evil let alone moral improvement.
How Do We Make Society Better?