"One issue is the narrowing of investment opportunities for working Americans." -- really? Only 54% of American's hold any form of stock at all, and most of those only have stock in the form of a mutual fund.

"Another source of disquiet is intensifying industry concentration." -- concentration or horizontal scaling? One of the things I disliked about working at Google was their claim they owned all my work at all times because they were literally in every single business associated with technology[1].

"Finally, there’s the societal benefit that stems from the institution of public capital markets." -- again what societal benefit is that?

Startups, and by that I mean venture based ones, not the local pizza restaurant or nail salon, absolutely would love to "go public" and have some nice liquid event. But they screwed a lot of people at the turn of the century out of their money and as a result that route was closed down. There are at least hundreds of companies that start, grow a bit, and get acquihired or otherwise consumed by big companies. The people then do their time (18 - 24 months typically) at BigCo and then roll out to do it again. If they could go public and take your money without consequence I'm sure they would :-).

[1] No, this probably would not hold up in court, but it was what legal told me when I asked them for a definitive statement.