This is incorrect. You start with the freedom to do whatever you like. Then copyright law (among others) comes along and takes away some of those freedoms. Then licences come back and return some freedoms to you. What you end up with is a combination of licence freedoms + freedoms copyright law doesn’t take.
This is why it is not part of most licence agreements to make backup copies of physical media you own, but this is often entirely legal. This is all heavily jurisdiction dependent - for example, fair use applies in the USA, while fair dealing applies in Australia. And it’s where the user is doing stuff that is relevant, not the designer.
It gets even more complicated when you realise you can’t copyright code - including gcode. Only the design that created it/it creates can be copyrighted, and even then a lot of it is going to be covered by expired patents (you can’t copyright any of the mechanisms in https://507movements.com/ for example, though you can use them in copyrighted designs), and active patents/copyrights held by others. That means while Disney could sue you over that Star Wars model you decided to sell, the person who designed it would be SOL.
Remixing is a VERY interesting case that I haven’t seen any of the sneakier things done with yet, but it’s only a matter of time. In many (most?) jurisdictions, it is not possible to enforce copyright in a way that prevents modification of a base media the user has a licence for. For example, if you buy a digital movie, and someone has made a list of times and replacement audio to create an abridged cut, this list and audio is not a breach of copyright, so long as it’s distributed on its own without the base media included. This is why game mods are legal, and not subject to the approval of the original publishers. It would likely be just as legal for slicers to allow ‘edit’ additions to models, that use the base model to create a remix based on a bunch of change instructions, whether the original designer wanted to allow that or not.