On the first look, the famous encyclopedia has a great quality. In the English version it contains of around 5 million keywords from all topics. The problem is, that it's difficult to find a subject which doesn't has an Wikipedia article already. For example, if we are interested in the topic of neural network, we will notice that an article was written already. Does that mean, that Wikipedia doesn't need help? No, it means that potential authors have to search more intensive to identify missing piece of information. The easiest way in doing so is to understand the difference between a popular encyclopedia and a scientific one.
Wikipedia is without any doubt a great popular encyclopedia. All the important topics are explained in well written articles. But it doesn't fulfill the standards of academic needs. The main difference is, that an scientific encyclopedia contains more keywords, especially two words keywords, and three words keywords. Let me give an example. In the normal Wikipedia an article is available about “Gaussian process”. It describes what the idea is, and gives references to external literature. For a popular encyclopedia it's a high quality article. The problem is, that Wikipedia doesn't provide an article about “Gaussian Process Kernels for feature selection” which is a very specialized topic. It has to with Gaussian process” but it is focus on a niche.
Highly specialized articles are needed in an scientific encyclopedia. Well written role models in the printed market show, that three words and four words articles are common in such encyclopedia. They are not simply introduce a topic to the newbie but they are written for an expert audience who has a certain information desire. This kind of content is missing in the WIkipedia today. The reason is, that a highly specialized article will generate a low amount of traffic, which means around 1 hits per day. On the other hand, it's more difficult to write such an article. This combination is equal to higher costs, which means, that in the past only a small number of such Wikipedia article were created.
What a potential author can do within WIkipedia is simply: He has to search for a specialized lemma and if it's not there, he should create a new article. Somebody may ask what the purpose is, to insert highly special keywords which are containing of two or three words. The reason is, that a domain can only be understand by it's specialized vocabulary. A detailed keyword makes it easier to approach a subject.
Let us describe the situation from a more abstract point of view. Wikipedia is great for general keywords like neural networks, robotics, or LSTM network. But it lacks on specialized vocabulary from within a discipline. That is the reason, why Wikipedia hasn't replaced academic encyclopedia.