I guess I can make this into a "historical method" post about these documents in particular.

The President John F. Kennedy Assassination Records Collection Act of 1992 demanded the full declassification and disclosure of every document with no exceptions by 2017. These 2021 documents are generally more complete versions of previous releases from 2017-2020. (You can confirm this for yourself by doing a Google search for the record number of each document, which remains consistent through releases.) What has happened with these 2021 documents is that in 2017, one of the intelligence agencies objected to some part of the declassification, claiming that the classified information still had relevance to an ongoing national security matter in 2017. In such cases, President Trump made a special exemption to the law on the grounds of national security. (For what it's worth, a lot of the new stuff that came out in 2017 related to the CIA's monitoring station in Mexico City. Conspiracy theorists are interested in that topic, but it wasn't necessarily withheld until 2017 as part of a conspiracy, and there was no "smoking gun" related to JFK in that release.)

In October 2021, President Biden demanded that each intelligence agencies submit a detailed explanation for each specific instance of ongoing classification by December 15. These 1,500 documents are the ones that the intelligence agencies did not bother to write up a concrete explanation for. So, what you can expect to see in this release are rather minor things, like the names of individual agents. Last week's release may be of use to researchers in the history of American intelligence operations, but most of the information in these files was already available in previous releases -- generally the 2017-2020 releases for these files in particular.

One representative new declassification is regarding a CIA assassination in the Dominican Republic, previously classified in this 2017 release. The 2021 version reveals a few new details on the CIA's use of a diplomatic pouch to supply handguns to to kill Generalissimo Trujillo. The use of the pouch was already revealed in another 2017 release, which makes this an extremely minor new declassification, but it is a violation of international law, and the declassified info indicates that the CIA concealed this operation from the State Department which was supposed to be in charge of the pouch.

If there is any really juicy information in the remaining JFK documents, the agencies have almost certainly submitted concrete objections to President Biden and that information will be withheld until December 15, 2022 when it will be reviewed again. For instance, the name of the CIA agent in charge of Mexico City operations during Oswald's visit there is still classified, although the other chiefs are declassified.