It's important to understand that while the number of citations of a publication is often regarded as a measure of the usefulness, impact, or influence of a publication, they don't exactly measure research quality, which includes credibility as well as the originality of the work, how a work moves a field forward, and the societal value of the work. A citation count can tell you about whether and how many scholars thought a work possessed credibility, but can't tell you whether popular trends influenced whether a work was cited or not, whether the journal it was published in influenced whether it was cited or not, etc. Citation counts are a widely accepted measure, and can be used, but should still be examined with a critical eye. Here are a couple articles that explain this in more detail:
