Hey there @EN6A6E! I understand the frustration. It’s usually not recommended to update projects to the most recently released versions immediately for commercial projects as there will often be some unforeseen issues.
For most assets that are cross version compatible such as 3D models (even without being flagged as such) can still be imported directly into the project by the Fab Plugin.
However there are assets that cannot such as code plugins or smart assets, however with smart assets (primarily blueprint) you may still be able to port them forward, but the process can be a bit harder. Loading them into a blank project of a previous applicable version then upgrading that project forward can often (though not always) preserve the assets functionality, and then you can migrate it to your current 5.7 project. (Note due to some changes Substrate and PCG can be a bit more troubleshooting).
If that isn’t working, when attempting to Add to Project inside the plugin, do the imports fail?