you could argue dmarc, dkim, and SPF were all invented as barriers to entry for small mail servers as the majority of internet SPF is permissive and the majority of DKIM is misconfigured. imo, senderbase and other reputation/policy proprietary shit-lists used by anyone with a Symantec or Cisco email product only served to convert the unwashed to a corporate license as most of these mechanical turks just paid the same spammers by night to show up in a delhi office complex day job to identify their own campaigns. DMARC and DKIM/SPF just wrapped email in a mandatory layer of arbitrary complexity to "solve" a problem that RBL's had largely managed to tackle as an independent entity.

that they exist in part to force the hand of small companies and users to simply submit to a big player for their email is something i have long considered.

DISCLOSURE: I proudly run my own email server.