Wikipedia is wholly unreliable for information outside the scope of leftism or contemporary media.

Surely some articles have a slant, but to assume that the vast horde of Wikipedia contributors are all 'leftist' is just absurd. Wikipedia is doing a great job overall at getting facts across in a neutral manner - if you have the feeling that's not reflective of your viewpoints then you could either question the source or you could consider whether your viewpoints do correctly fit to the facts. It's very easy to dismiss sources that don't fully agree with your views, but that prevents you from ever strengthening or improving your views.

Have you reviewed Wikipedia's reliable source list [1] and quantified left vs right sources? You will be pleasantly surprised.

1 - https://en.m.wikipedia.org/wiki/Wikipedia:Reliable_sources

Perhaps its because there are numerous sources excluded when they fabricate information or mislead.

I know usa politics are nuts, but drug reactions is not a partisan left vs right issue.

If one wants to get facts about drug reactions (for example) then sure, there will be articles in reputational journals reporting on studies (that should be objective), as well as straight up reporting, like the adverse reaction data. But as soon as you want context or analysis on how to interpret the information and what to do about it, opinion and world view are involved. There may also be legitimate or groundless views about the trustworthiness of figures reported, potential cover up or under reporting, etc. This all gets magnified when it's about a topic that is being used as rhetoric to change people's behavior.

Yet leftist websites are known for silencing any reporting of negative drug reaction among the hundreds (or maybe thousands) of other issues on their agenda.

This includes ones ran by infamous Dorsey MD and Zuckerberg MD.

For example, the first two reports of unfortunate Michigan boy died from heart muscle bag inflammation vaccine side effect resulted in two bans.