Invidious functions as an ad blocker - not that you should not already be using one. This feature is useful when sharing videos with others who are not necessarily blocking ads themselves.
Invidious provides Atom feeds and an internal subscription system which is one step away from Google's prying eyes.
Sponsorblock supports Invidious.
The Peertubeify extension can redirect Invidious links to the same video hosted on Peertube if available.
Nitter is another project that does the equivalent for Twitter.