Wikidata and quality, typically they complain that both quality and quantity is not good enough. The reality though is that it is its qualities that makes Wikidata function in the first place.
When people ask: "When will Wikidata be good enough to be used by Wikipedia". They fail to appreciate that its first achievement was to bring improved quality to Wikipedia's interlanguage links. Every Wikipedia does benefit and uses Wikidata.
These interlanguage links can be improved on. Many articles and items should be merged. Research supports this as a fact. However, items can only be merged when they are on Wikidata. The Chinese item for the "Quercus robur" was merged because someone had added the name as a label. It is therefore a quality when articles have a corresponding Wikidata item and are enriched with statements and labels.
Many items link to external sources. For many items such links are yet unknown. Often the external sources know about links to Wikipedia and when we collaborate, we can add all of them as items to Wikidata. It increases the quality of Wikidata. When Wikipedia articles have been missed, they can be merged to improve quality even more.
Some statements are made by bot and others by hand. James Schlesinger died. Many new statements were made. Statements were made to other people who were "United States Secretary of Defense". The web of information grew and with it the quality of Wikidata. Dexbot is adding claims for "is in the administrative-territorial entity" for items that Wikipedia knows to be in the USA. It grows the web of information in a spectacular way.
When you wonder why a Reasonator is succeeding, why a WDQ makes a difference, it is because Wikidata is increasingly valuable. Its value is in the sum of what it connects. When you assess the quality of Wikidata, it is obvious that there is more to connect. It may be obvious that many connections are redundant. The relevancy of Wikidata however is in the great amount of data that is added all the time, that gets connected all the time, that gets merged all the time.
The question when Wikidata will be good enough to be used by Wikipedia has an answer; it has been used from the start and as time goes by more subsets of information will be better represented in Wikidata than in any Wikipedia.