The Prusa kit is a kit in every sense of the word.
Here are the assembly instructions: https://help.prusa3d.com/category/original-prusa-i3-mk3-kit-assembly_336
I had no experience with 3d printers but it only took roughly one day to put together.
The instructions were easy to follow and the machine takes care of a lot of the calibration stuff itself.
At one time 3D Printer kits came with a couple bags of electronic components, some PCB boards, stepper motors, belts, bags of specialty parts, bags of screws and nuts, and some machined parts that you hopefully didn't have to drill carefully placed holes in. You had to solder the pieces onto the PCB boards and put together everything.
They reminded my of the original Heathkits that used to be sold.
They were also kits in every sense of the word. I bought an electric motor kit one of my grandkids and gave it to him at Thanksgiving. The one I got when I was a kid required me to wind all the copper wire into coils etc... and it took me hours to get the thing put together. I gave the little motor kit to my grandson and he had it put together before we finished putting food on the table. It was not the same thing although the final result looked very similar.