I frequently encounter Gravatar criticism due to its locked down nature. It’s super easy once you’ve signed up, but not everyone wants to sign up with WordPress just to have a globally recognized avatar, especially not immediately after they’ve just signed up with some new website that tells them “want an avatar? Sign up over here as well why don’t ya!”
Here’s how a better Gravatar could work:
In an e-mail to (email redacted), either upload an image attachment or include a single link to a direct URL for an already uploaded image (e.g. on imgur).
You now have a globally recognized avatar tied to your e-mail, active with any platform that integrates this service.
No registration required. Would also work with email aliases.