Unfortunately, as you know, I adhere to the position that "only the best are universal." I use models and give them a worthy application in my maps, without missing the opportunity to say a good word about the model's author and include them in the list of acknowledgments and promote them somewhere if there is an opportunity to do so, unless their identity is hidden behind a veil of secrecy, of course. But I won't do it myself for two reasons:
1) My list of map modders is so huge that the activities there alternate anyway, one season of one thing, one season of another, then back to the previous season, etc. If I add such a time-consuming task as creating models, I'm afraid everything will become even worse.
2) Unfortunately, I don't enjoy this activity, although I've even tried it in more than one game. Besides, it's still worth separating roles. Some people create models, and some create content with these models. After all, game developers clearly don't have 3D modelers writing campaigns and code.
In general, that's my position. I think it's understandable. But nevertheless, there are those who do both. But there are very few of them.
Added 31 seconds ago
yes, I was talking strictly about myself.
What I wrote above is addressed to you as a map modder; consider that it doesn't apply to you as a level designer. I'll even say more: as a level designer, you can safely 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 whole problem is that their skills are not universal, but often focused on one or another genre of games, and that it is more difficult to evaluate the work of a level designer than the work of the same modeler or animator.
What I wrote above applies, as I mentioned in the text, to people who modify the "visual" side of the game.
It is them that I urge to "create their own." And here it is not a question of which position is "correct," but a question of whether we want to develop or not.
I repeat once again, you, as a level designer, do not necessarily have to create your own assets in order to develop; you create your own maps, but, for example, a modeler must definitely create something completely original at a certain stage in order to develop.