I have nothing against any meta search engine, they are very useful, and I use them primarily as well.
However, they are not a true alternative, because they depend on third-party services. The same as Invidious is a very useful, but also not an alternative to YouTube itself, just a different user interface.
It was Russia and other autocracies etc. that diminished the trust by actually financing developers for multiple years to first earn trust and finally introduce backdoors into open source software, as demonstrated by the XZ utils backdoor.
In open source projects, maintainers need to have some initial trust into each contributor, and let this trust naturally grow with time and contributions. They cannot perform intensive background checks on everyone before accepting a patch.
While it is easier to uncover backdoors in open source software, there is no good way to defend and prevent against this kind of attack in this type of development process. All open source projects can do is trying to take away some trust from people within higher risk groups. This of course might lead to discrimination.