At the end of the nineties, the early days of the internet it was, until some point at least theoretically possible to read all of it. Then, just all of the personally interesting content. Today, it's hard to get through just the comments for whatever new content I'm following.
I remember going through the dmoz directory around the end of the millennium. Going through categories. Drilling down to the interesting parts. I think I ended up with thousands of bookmarks out of it. I have to admit most of those were left unread. There was just that much new content coming up constantly.
Before it's shutdown in 2017 it had over 5 million links. Hand curated and categorized. Similar number of pages as the English language Wikipedia has today. Still too much to read through in a single lifetime. Mostly boring stuff as well if you ask me. But there is still a lot of interesting thing as well.
Some topics are interesting enough to drill all the way down to the smallest details. But besides randomly stumbling down to such pages it's hard to find them. There is also the vital article pages, listing just the top 10 most important things in level 1 down to 50 000 articles at level 5. Those should already cover the essentials to get started.