Indeed! But the APIs that don't require an access token are abused. Heavily. Some people are sending hundreds of thousands of requests per day, sometimes requesting the same feed once a second; ignoring the HTTP/429 responses we send back; jumping IP when they get blacklisted etc...
We thought about making authentication mandatory for all APIs, but that would have been a bit severe.
So we now limit the data you can fetch without an access token to the last 50 entries at most, with no continuation. This is consistent with what an RSS feed offers in the first place (you don't get access to the full article history). The rate limits are also stricter than before, and enforced more aggressively.
I hope this clarifies the changes you are seeing.