I'm using Lineage myself and completely agree on that point.
However, also @EskeRahn is right in that "certification" of a software does not necessarily mean that the software in question is technically superior to any other. It just guarantees that it fulfills the requirements of a certain defined standard in terms of configuration and behaviour.
Technically, my self-built LineageOS 16.0 is, both, more capable and more secure than Stock Android 9: unlike the latter, it contains the latest security patches and the many feature enhancements implemented by the LOS community and mysel