HDDs seem to be fickle little ■■■■■■■■, I’ve had bad luck in the past with big slow downs after just a few months of buying & installing a new one.
From what you’ve posted it does sound like the same issue I had, disk speeds accessing and writing to the derived data cache were slow, so when loading a new asset the editor would spend ages writing to the DDC. Took me hours to open all the kite demo assets, for example. If you have one, moving the derived data cache to an SSD can help a lot, as that’s where the editor will do most of it’s disk-based work afaik. Even moving it to a HDD that isn’t being used by other programs while you’re working might help, so the editor doesn’t have to contend with the OS & others for file access.
Other than that I’m not sure there’s much you can do to avoid that particular issue. Wish I had better advice on that, I know how much it sucks and destroys productivity.