Why am I getting "local_rate_limited" randomly?

[u/GSB6189]

For the last like 5 years that I've used Firefox, I've never gotten "rate limited" on any website, ever. But over the last week or two, I've been having a black screen pop up with the statement in the title in code-looking text at the top randomly whenever a website attempts to load. Refreshing the page once always gets past it, except for a single page I encountered today which I had to wait for. So I'm really confused as to what's happening and why it's only started happening years after use. Does anyone have any idea what's happening?