25,430,779 items any approach to quality will have a potentially negative quality effect when quality is approached from a different perspective.
Yet, we seek quality for our data and aim for quality to measurably improve. There are many perspectives possible and they have value, a value that is strengthened when it is combined with other perspectives.
At the Wikimedia Foundation, the "Biographies of Living Persons" or BLP has a huge impact. When you consider this policy, it is about biographies, a Wikipedia thing and this is not what Wikidata does. It is important to appreciate this as it is a key argument when a DLP "Data of Living Persons" is considered. Important is that the BLP focuses on articles for living people and its aim is to prevent law suits from articles that have a negative impact on living people.
Data is different, it is used differently and it has an impact in different ways. Take for instance notability; a person may be notable and relevant because of having held an office or receiving an award. In order to complete information on the succession of an office or an award, it is therefore essential to include all persons involved in Wikidata. At the same time, when information is incomplete it can have an impact on a person as well. "you did not get that award because Wikidata does not say so".
Wikidata is incomplete and immature. Given the different perspectives on a DLP, most of them are not achievable in short order. The people who insist on a "source" for any statement will wipe most of the Wikidata statements and force it to a stand still. The people who insist on completeness have an impossible full time job for many years to come.
So what to do? Nothing is not an option but seeking ways to improve both quality and quantity is. A key value of Wikidata is its utility. The "Black Lunch Table" is one example of giving utility to Wikidata. They use Wikidata to manage the Wikipedia articles they want to write and expand on the notability of artists by including information on Wikidata. All the information helps people to write Wikipedia articles. Quality is important. Being included on the Black Lunch Table means something; artists are considered to be notable and worthy of a Wikipedia article.
Another example is using the links to authors so that people can read a book.
Given the size of Wikidata, it is impossible to get everything right in short order. When we can get people to adopt subsets of our data, these will grow. Our data will be linked. When we get to the stage where people actually object to data in Wikidata, we have improved both our quantity and quality substantially. As it is, looking at all the data, typically there is little to object to and that is in itself objectionable.