It used to be IRC, but that's also a little bit centralized.
You mean "massively worse": IRC was a single system that you had to stay connected to when you were online to get returned by it. If it filtered the view you got, then that's the view you got.
The dnseeds don't require any connectivity to it, and there are a bunch, so any one can't rig your view of the network. Your ISP's recursive resolver hides your IP from the DNSseeds and can cache requests so the seeds may not see your request at all. Plus, now adays, it only uses them if it doesn't have its own info and/or is failing to get connected.
The IRC server started tampering with the results too-- they had some weird justification for it, but that was a major factor in moving to the dnsseeds.