For example, you can clone a repo from GitHub into your workstation,and then clone that repo into multiple folders in your workstation where you unleash agents to implement changes. The you pull those changes to your local repo or even directly to GitHub or GitLab or whatever. That's pretty decentralized.
Now, compare this to the god awful mess that was subversion.
GitHub is still a single source of truth in that scenario.
BTW, it's unclear what exactly you think is wrong with SVN. Works great when used properly (like any tool, you know).