Realistically speaking, Yahoo was a gatekeeper between content and audience... same as every advertising agency, broadcaster, studio, record label or radio station everywhere. They were the first ones to attempt to brute-force an index by exploring the web by hand, back when two college kids could reasonably do that. This allowed them to get to the mountain first, but it didn't keep them on top. I've always been lukewarm towards Yahoo because they never indexed the shit I cared about - for my searches, they were thoroughly useless. It was either altavista.digital.com or, far more likely, go2net.metacrawler.com - metacrawler being the first brute-force "let's see what a half-dozen search engines tell you and then we'll weight it" approach to search engine mechanization. This allowed you to see that Yahoo sucked, Ask Jeeves was comically bad and then, for two brief months, holy shit this Google thing was effective. Then Google blocked go2net but it didn't matter because there was no point in using any other search engine. Go2net went from $130 a share to delisted in the space of six months. That was Yahoo: a hand-crafted index of plain vanilla search results, by people who could use the Internet, for people who couldn't. Really, it's a testament to their vitality that they're still around, considering they became irrelevant not long after people got sick of hearing "You've got mail!"
Yahoo wasn't bad for the case of "I know this thing exists, and that's about all I know about it. I want to fix that.", like a lot of people use wikipedia for now. You wouldn't get deep into anything off the beaten path, but you could usually learn enough to go digging.