I'd disagree with this though - I'm an elder millennial and there was plenty of information available online - I mean the trading the stockmarket thread in this very forum is now 15 years old so I'm not sure you can blame lack of info so much as lack of curiosity.
Halifax Sharebuilder was launched in 2001 - you could have literally walked along your local high street and asked for info but Google would have revealed far more - there were a bunch of online/discount brokers available from the late 90s onwards - places like Hargreaves Lansdown, Fidelity, Charles Schwab would give you access to funds (including Vanguard) and individual equities.
One of the main sites for info was the motley fool or fool.com (also advfn and interactive investor), all of those had BBs/forums just like this one in the early 00s. I bought this book back in the 00s, this is the *third* edition from like 2002, fool was launched in 95 and the UK site in 97... their whole thing has literally been promoting the benefits of compounding and emphasizing how saving early is great.
This stuff *was* available back when you were in university, you only needed to open up google and find it.