Well, it depends on how you look at it. From my perspective as a card creator, who, for example, simply needs a model for a video, using someone else's work is the best option. For someone who is specifically focused on creating models, making their own is, of course, the best path to progress, especially now that, as I understand it, all the necessary tools are available. Ultimately, it would be best for these two people to join forces to create the final product...
But if we're talking about it on a deeper level, yes, the motivation for people to create their own work is a good thing, but firstly, what is the purpose? In my opinion, such motivation needs a clearly defined end goal. Secondly, are there enough people in the community who are capable of creating something comparable to the work of professional developers?
What I wrote above is directed at you as a card creator; consider it irrelevant to level design. I'll even say more: as a level designer, you can freely use your locations and maps assembled from a set of other people's assets in your portfolio.
It's a different kind of work.
But for a level designer, it's much more difficult to break into the industry. The problem is that their skills are not universal, but often tailored to a specific genre of games, and that it is more difficult to evaluate the work of a level designer than the work of a modeler or animator.
As I mentioned in the text, what I wrote above applies to people who modify the "visual" side of the game.
I am urging them to "create their own." And here, it's not a question of which position is "correct," but whether we want to develop or not.
I repeat, you as a level designer don't necessarily need to create your own assets to develop; you create your own maps, but, for example, a modeler must eventually create something entirely original in order to develop.
Regarding whether there are enough people: for starters, one or two is better than nothing.
Regarding the purpose: it's interesting. It's creativity. It's development. You can find a good job with good skills.
In short, the answers will be the same as to the question, for example, "why paint?"
Added 9 minutes later
Actually, as I understand it, creating new models and new animations is not that difficult.
...
I don't know if I'll delve into all of this, but I'm quite interested.
It's as difficult/easy as, for example, painting. It's just a form of creativity.
Interested? Why not try it. You can start with a tutorial on modeling/unwrapping/painting a chest from a clumsy modeler. The link to this tutorial is in the post where I list the modeling programs. The clumsy modeler leads the tutorial in a fun and simple way. If you need anything, good luck. Feel free to ask, I'll be happy to help with advice