Millions of businesses, 'knowledge workers' and infovores rely on RSS for their daily workflow and learning, without which they'll have no other reasonable alternative to stay updated with decisive information and insights for high-volume, high-frequency, low-noise Web content.
Starting from Google Reader's shutdown to Firefox's removal of RSS support, it's just that these consumer vendors have not been able to leverage its business use-cases. It's a feature for them that they couldn't monitize, because that requires a different tool-set, which is not their primary product.
RSS is a backbone, much like a simple API, but it was touted as a front-end enriched with ads, analytics, widgets etc., that didn't/can't work for the casual consumer.
RSS ecosystem is alive and healthy for it's vast and core audience, irrespective.