pretext Is it possible to recover data from fastboot?
If the issue is a flash storage failure, it is possible that a commercial forensic data recovery service might be able to restore some data, but not certain.
It is also possible that wiping the user data partition via Recovery might restore the device to regular operation (without your data) for some time, if the flash system reroutes to avoid the bad spot. But if one part of the flash has gone bad, and it's an old device, further failures are plausible. This is more likely if the storage was heavily used (lots of downloaded content, lots of video recordings or pictures taken).