The only "third-party" packages that we want to ideally allow/support would be provided from LTS versions of our runtime (in this case, packages provided by the dotnet team and audited by microsoft). So we will always try to build around what the framework provides. Second choice is our own code, third choice is open-source packages, fouth choice is a separate application/appliance (lets say ZenDesk for ticketing). Over time, we will reduce this footprint to only have dotnet team code and our own.
Remember most CVE's can be hidden on servers that are not publicly routable and don't have a real exploitation paths. The bits that are public (lets say a linux edge server with a web server on it, some firewalls, a couple of open ports) - these should be hardened to the max and not allow full access to all the services running behind it. We don't even give our internal services public IP addresses to make near impossible to route traffic to them.
Our git repo's are also not on public infrastructure (serious, think carefully about hosting on public services and if you really need it), never mind making the repo public.
We also have a dedicated secrets/certs manager, so no credentials are in codebases or pipelines. Very strict in this regard.