Wikipedia strives to be a serious reference resource, and highly technical subject matter still belongs in some Wikipedia articles. Increasing the understandability of technical content is intended to be an improvement to the article for the benefit of the less knowledgeable readers, but this should be done without reducing the value to readers with more technical background.
Making articles more understandable does not mean that detailed technical content should be removed. For instance, an encyclopedia article about a chemical compound is expected to include properties of the compound, even if some of those properties are obscure to a general reader. But often summarizing highly technical details can improve the readability of the text for general readers and experts alike. For example, a detailed derivation of a result is unlikely to be read by either a general reader or an expert, but a short summary of the derivation may convey a sense to a general reader without reducing the usefulness to an expert reader. When trying to decide what amount of technical detail is appropriate to include, it may be helpful to compare with a standard reference work in the particular technical field to which the subject of the article belongs.
It is also important not to oversimplify material in the effort to make it more accessible. Encyclopedia articles should not "tell lies to children" in the sense of giving readers an easy path to the feeling that they understand something at the price that what they then understand is wrong.