When this happens, you can no longer get content from the RSS Feed.
The ban could be temporary or permanent depending solely upon the RSS publisher.
For example, an RSS Feed might have a maximum polling frequency of 60 minutes. If you attempt to check the feed for updates more frequently than the specified limit, the RSS publisher can suspend your access temporarily or cancel your RSS Feed subscription.
Many RSS Feeds use messages that contain a brief summary of a larger message or an article with a link to the full content.
You can configure Outlook to automatically download the linked content as an attachment to the RSS messages.
So if you don’t have any requirements to do authentication on the RSS and you’re in love with XSLT, the web part is there for you my friend!
Another options is to use the Content Search Web Part. Share Point 2013/Online supports the creation of Result Sources using the Open Search 1.0/1.1 protocol.