Well, there is some accountability penalty in the DMCA, but it's just against people who issue takedowns for content they know they aren't responsible for. In other words, the only penalty is for impersonation, not for totally frivolous and excessive claims.

There is some merit in limiting who-can-file-for-what, however it also annoys me since it also closes off a route of activism which could help force a consistent application of the rules. (Thus exposing both how bad the system is and also forcing rights-holders to curb their overreach.)

For example, imagine that AcmeCorp lawyers were to abuse takedowns to remove negative reviews of their product, while ignoring positive reviews that are equally-or-more "infringing." Or if multiple companies arranged a kind of ceasefire-cartel while using the law to persecute others. If a citizen could "help" them with removing all that content they "missed"...