Establishing the truth of a proposition, however obvious, as this is, is not the purpose of Wikipedia, nor the purpose of categories. Categories are an aid to the reader to in finding information.
I don't understand the dichotomy you seem to be trying to uphold. Wikipedia provides information but not truth? What is truth?
Here's the start of our article on the Eiffel Tower:
"The Eiffel Tower ... is a metallic tower built on the Champ de Mars in Paris ... and is nowadays the most famous landmark and symbol of Paris."
This is information. And truth.
When we say "Homeopathy is a pseudoscience." we are also providing information by writing down a true statement. If I may paraphrase a couple of sentences from a certain sci-fi franchise:
"The first duty of every Wikipedian is to the truth, scientific truth, historical truth and personal truth. It is the guiding principle of Wikipedia."
When reasonable people interpret available data in different ways we try to describe each position fairly.
Then there are some unreasonable positions. Those are usually dealt with in separate articles and otherwise ignored. Here's an excerpt from the start of the [[Apollo program]] article:
"Project Apollo ... was devoted to the goal of landing a man on the Moon and returning him safely to Earth within the decade of the 1960s. This goal was achieved with the Apollo 11 mission in 1969."
There are many people who disagree with this but since their position is unreasonable it is not dealt with in the main article but relegated to a separate article. Now, *that* article will try to fairly present the views of those who believe that the Apollo program was a hoax. However, by choosing to privilege the reasonable view in the main article Wikipedia has *already* chosen a position, whatever category the hoax article is put into.
Or let's take [[Earth]]. Here's an excerpt from the lead:
"The planet formed around 4.57 billion (4.57×109) years ago and shortly thereafter acquired its single natural satellite, the Moon."
There are many people who disagree with this. We try to describe their positions fairly in separate articles, e.g. [[Creationism]]. The article on creationism may try to be scrupulously fair to the creationists but the bottom line is that Wikipedia has *already* acknowledged the scientific facts as superior to the creationist theories (at least the "Young Earth" variety) by including them in main articles like [[Earth]].
Including [[Creationism]] in [[Category:Pseudoscience]] is just icing on a cake that has already been baked.
Regards, Haukur