The modern concept of knowledge is an anomaly. The notion that knowledge is something that can be found on a sheet of paper, in a book, in a hard drive, in the digital cloud, this is not the kind of knowledge that the Islamic tradition is based on.
True knowledge cannot be abstracted away from living, breathing people. For example, Allah sent revelation by way of the angel Jibreel to the Messenger ﷺ. The Prophet was illiterate, so the only way and the best way to pass his knowledge was through companionship — namely, by teaching his companions, who took instruction not only from his words but also his actions, his behavior, his blessed manners, etc. Human beings are thus the conduits of knowledge and the Islamic tradition has operationalized that through the concept of isnad.
To claim to truly know something of `ilm, i.e., what Allah has revealed, one has to know all the persons through which that knowledge has passed over the centuries until it arrived at you by way of your teacher. Reading from a book or the internet is not a substitute for this. At most, one is merely familiarizing oneself with texts, which, don’t get me wrong, has its own benefits if done correctly. But to be an `alim, to speak authoritatively requires isnad. This is how Allah has preserved the deen.
And this is why the Prophet ﷺ said, “Verily, Allah does not take away knowledge by snatching it from the people but rather he takes away knowledge with the death of the scholars until he leaves no scholar behind and the people turn to the ignorant as their leaders. They are asked to give religious judgments without knowledge, thus they are led astray and lead others astray.”
We can contrast this with the modern conception of knowledge, which usually has no moral component and can be abstracted as separate from people. Go to a university physics class and see if the professor mentions any history, where those formulas have come from, who taught them to whom, and so on. Perhaps that disconnect with history is fine for the sciences, but not for one’s religion. The source of all deeni knowledge is in the past, so to cut ourselves off from the past is to cut ourselves off from that knowledge. Muslims have to be careful not to conflate the modern, scientific understanding of knowledge with true religious knowledge.