Google Webmasters said,”We’ve had to drop the public submission feature.” The company did not say why it was necessary to drop it. Maybe it has to do with spam issues or abuse. Google added, “… but we continue to welcome your submissions using the usual tool in Search Console and through sitemaps directly.”
The last time Google updated the submit content tool was back in 2012, when it moved it to the classic Google Webmaster Tools URL.
Google says webmasters should submit content only through Search Console’s Fetch as Google tool or via sitemaps.
We've had to drop the public submission feature, but we continue to welcome your submissions using the usual tool in Search Console and through sitemaps directly.
— Google Webmasters (@googlewmc)