I'll share, since it is killing me playing 1.13 without what i consider my essentials. I'm a vanilla tech player, but after so many years of playing there are certain mods I can't live without, and wish they were part of the game:
-Bounding Box Outline for wither skeleton farm marking/creation
-Village Marker for seeing to it your stacked iron farms are building properly
-BetterPVP to see creatures health at a glance. Great way to spot a low health villager, or know if things are getting damaged during transportation
-Inventory Tweaks: 100% essential mod, I hate the game without it now. Time is precious, and a well sorted inventory/chest makes me happy. I'm itchy without this mod haha
-Light Level Overlay (reloaded): 100% light caves and surfaces without wasting too many torches, and easily spot those areas that need more attention. I miss my F4 button almost as much as middle click sorting with Invtweaks
-TapeMouse: easier to use than actual tape, and lets you keep using the PC while afking in the background. I've since found a nice windows mini script/program written explicitly for MC that does the same thing, allowing auto button manipulation while working elsewhere on your PC. But setting it up via command is easier
Others that are not as critical, but still use are Sound Physics + ambient sounds, WorldDownload, Optifine, World Edit, and schematica
I wish we had a forge 1.13 progress bar to cheer on :)