It should be save to reuse your households and lots from your library. So, if it's still possible with your old saves, you might save all your creations in CAS or build mode to your tray folder and copy that tray to the new save. Keep in mind if you use CC items with your sims and builds, those items must also be available in your new mods folder, because they are not a part of the tray folder objects and the game is looking for them in the mods folder.
But also keep in mind that while restoring your game that way from the tray, all relationships and achievements of the households will be lost. Those attributes can only be restored with a complete and functional backup file set.
You can also export your sims and lots from your tray folder to zip files using the "Sims 4 Tray Importer" tool (S4TI). S4TI also copies the CC in use with the respective object into the zip archive. This even doesn't require a running game, only the tray/mods folder at the correct location (given that you already saved your lots/hh in your tray).