Sure, in the long run it all works out, but in the short term there's quite a lot of turmoil.
That said, most of the named business lines are those particularly easily replaced even if the threat of other VC-backed businesses coming into the market still exists: those inclined to open sandwich shops or market themselves as handymen aren't likely to be too worried about more online threats emerging in future, and the savvier ones are instead figuring out how to get profitless startups to provide them with low cost marketing.
I don't see how that's a controversial point, but it's a distinction that a lot of people who aren't in tech, or around startups don't get.
As for the startups, I think your comparison of Amazon and Pets.com is astute. For each of these companies, are we looking at an unprofitable early stage of a company that will eventually become profitable (e.g. Amazon, probably Uber) or are we looking at a company that can probably never become profitable? The former seems fine even if it causes some temporary disruption, but the latter is just waste.
A VC once told me that he thinks most venture funds don't really stand a chance of making money at all. The reason they have money to invest is because there's such a surplus of cash from institutional investors who need the "venture capital" checkbox. The lower-end VCs don't get the best deals and have to settle for leftovers, so their chances of getting lucky in a get-lucky business are that much lower.
At any rate, no honestly run pension fund is actually putting its capital at significant risk by tossing a few tenths of a percent at a collection of VC funds.