If you prefer to use an RSS feed for a content source, you can still use Google Analytics to prioritize content within the feed and publish your highest-performing content first.
When creating a Website Feed using RSS, find the dropdown for "How do you want to pull content from the feed?" Select "Highest Ranked by Google Analytics," then choose a Google Analytics view that you have already onboarded to optimize the feed order.
You will be able to select the feed in Planner, and will see indicators of the number of page views each item has received. You can then schedule content from the feed by dragging and dropping it into Planner, or use the feed in an Autopilot slot or block.