The people you see using the term are likely not using it properly.
M-W's definition:
a: relating to or characteristic of a whole group or class : GENERAL b : being or having a nonproprietary name <generic drugs> c : having no particularly distinctive quality or application <generic restaurants>
I'd think of this as being a 34" scale bass with four strings and a pickup. They all have that in common, at least the electric ones do.
If I were to expand that any further to include my personal OTTOMH idea of "generic", I'd say a passive P-Bass, starting (in quality) around Fender level and going down a step or two from there. Anything above that, I'd consider "higher-end" and anything well below that I'd consider "crap".