11 We have much to say about this, but it is hard to make it clear to you because you no longer try to understand. 12 In fact, though by this time you ought to be teachers, you need someone to teach you the elementary truths of God’s word all over again. You need milk, not solid food! 13 Anyone who lives on milk, being still an infant, is not acquainted with the teaching about righteousness. 14 But solid food is for the mature, who by constant use have trained themselves to distinguish good from evil. (Heb. 5:11-14)
These thoughts from N.T. Wright:
So why is it, in the twenty-first century as in the first, that so many Christians are not only eager to stay with a diet of milk, but actually get cross at the suggestion that they should be eating something more substantial? This is a question that has puzzled and bothered me for years. In my own country I meet a settled prejudice, even among people who are highly intelligent in other areas, who work in demanding professions, who read serious newspapers and magazines and who would be ashamed not to know what was going on in the world, against making any effort at all to learn what the Christian faith is about. As a result we find, both inside the churches and outside, an extraordinary ignorance of who Jesus really was, what Christians have believed and should believe about God and the world, how the entire Christian story makes sense, what the Bible contains, and, not least, how individual Christians fit in, and how their lives and their thoughts should be transformed by the power of the gospel. There are many places in the world where there is a great hunger to know all these things, and an eagerness to grasp and take in as much teaching as one can. Some Christians are indeed eager and ready for solid food. But I deeply regret that, in many churches in Western Europe at least, it seems that the most people can be persuaded to take on board is another small helping of warm milk.
Wright, T. (2004). Hebrews for Everyone (p. 52). London: Society for Promoting Christian Knowledge.