They are literally the only UK daily newspaper not owned by some rich owner or conglomerate, and about the only newspaper (along with the observer) that does not publicly support one of the two main political parties.
And 2018 study found the guardian was by far the most trusted of the uk daily's, and second only to the bbc as a news source https://www.pewresearch.org/journalism/2018/10/30/western-europeans-under-30-view-news-media-less-positively-rely-more-on-digital-platforms-than-older-adults/
but yes, im a Guardian reader so maybe biased. but theres a reason I read them, and not another.