I don't think startup investing is for everyone, for some of the reasons you mention below. And I agree there's a risk of the ecosystem developing poorly to be a "market for suckers". But I think the JOBS Act is a net good thing and the concerns you highlight are addressable.
The main problem I have with the "old rules" of investing is that wealth is used as a proxy for sophistication. If you happen to have a PhD in Machine Learning, for instance, you're unable to invest even $100 in AI companies unless you're literally a millionaire. With companies staying private longer, most of the growth in high growth startups is only available to the wealthy. From the data we've seen so far from unaccredited investors trying to invest in startups (but failing the financial requirements) we haven't seen any correlation in financial status and savviness. Unaccredited investors try to invest in the same companies as the accredited investors, and they all avoid the weaker startups. So I'm optimistic about that, at least for the early adopter crowd. And I think as the ecosystem matures fundraising platforms will look less like Kickstarter campaigns and be more optimized for groups of people assessing/vetting startups. (But I'm an optimist and obviously biased.)
The biggest problem with the JOBS Act is the potential for adverse selection. If "the best" startups don't want to touch it with a 10-foot pole for legal reasons, that's a serious issue for the ecosystem. We've been spending a bajillion dollars on legal research and think we have something that makes this nearly a no-brainer for startups, but time will tell. Startup lawyers hate being guinea pigs with new regulations.
At best I think we'll see a lag in mainstream startups using Title III. Instead we'll see small businesses that are underserved by current investors first. With more precedent and familiarity with unaccredited crowdfunding I'm pretty sure we'll see more startups use it. A similar thing happened three years ago with "rich person" crowdfunding – many critics speculated only bad companies would use it, not-bad companies started using it, and now it's generally accepted.
Index funds would be great. The JOBS Act prohibits investment funds explicitly and it's prohibitively expensive to create a fund for early stage startups that unaccredited investors can participate in. However we're working on ways to emulate index funds, and I think it'll be doable by someone in the long-run.