This is probably because the DXF file imported contains a large number of drawing entities (lines, arcs). I've tried to use DXF files as "input" for designs, like customer layouts of their facility or machines, but have found it impossible to work with the data. Thousands of lines that are fine for a dumb data file, but when I try to use them in a sketch, Creo adds dimensions for every entity, which results in a very slow and useless file.
I have found that it's more manageable to just extract the info I need from the DXF and move on from there.
