It should be impossible to change a license to a less open version, just like Printables does. There a license freedom is irreversible. But even then I think it is absurd how many people list their models as exclusive for the couple of cents. It completely destroys the community vibe.
But it’s also a very bad incentive for how you list (or not) remixes. I am looking for a mask to possibly remix for the contest, and I see multiple Guy Fawkes masks. Both “exclusive models” but both remixes/copies of this one on thingiverse: Guy Fawkes Mask by Jtm - Thingiverse
Exhibit A:
This is just a blatant copy, the JTM logo is still in the corner. But it is listed as an original, exclusive model. This ‘designer’ is luckily too stupid for his own good with not erasing the logo, but the model has been up for 5 days and nobody cares.
Exhibit B:
This is a low poly version of the same model. But the problem is, it’s hard to check. And it is by a designer with 650 followers and 94 models. But I overlayed the models in the slicer and you can clearly see that it is the same model:
With about 350 downloads and 50 makes.
The original model requires to give attribution and also prohibits commercial use (and in my eyes the exclusive program earns you money and thus is commercial use):
So the issue is not only that material is less likely to be remixable but also that there is less incentive to correctly post remixes, making it stealing/copyright infringement.
I am not sure what the right course of action is with the above models and the likely hundreds/thousands more on this platform but as a designer myself this theft incentive and fenced off exclusivity program just rubs me the wrong way.