We could call them ‘spam cans’ but they really ARE oscillators by definition. 
This is all my preference and opinion, as @transistorcat said there is no wrong or right way to do this stuff.
The majority of my body of work is generative visual synthesis - making controlled shapes.
For that purpose I consider only the following as workable PRIMARY signal sources for my workflow:
- Video rate Oscillators
- Ramps
Secondary processing is important, modifiers like frequency multipliers (Staircase) and operators (Arch) and multipliers (Faders, key’s, etc) can combine the two primary signal sources in myriad ways.
Then modulators like LFOs/function generators and sequencers. These are most of the modules I have from the audio world. And MATHS 
While I do use feedback in my work, It’s either pure feedback outside the synth or as a modulator (both direct and re-entrant*). I don’t find that feedback is controllable enough to be a primary signal source for generative synthesis, so for me it can’t replace any primary sources.
*edit: Direct feedback is patching the output of a module back into one of it’s modulation inputs, directly or through other modules. Re-entrant feedback is taking the encoded signal back into the synth.