A critical issue.

Since we're talking about filler episodes, let's abstract from this discussion and the specific title. I've seen online countless times the opinion that filler episodes in series or cartoons are bad and don't deserve to exist.
Of course, I don't agree with that. If you prefer to see sooner rather than filler episodes how another very original hero defeats all enemies for the hundredth time, marries a classmate, or dies, then you are probably still young, and this is all new to you.

The point is that filler episodes are not all the same. In shonen anime, for example, they often consist of a series of battles with some random antagonists, seasoned with a couple of gags and a weak plot. A plot that doesn't add anything new to the development of the characters or the main plot. At the same time, the battles themselves are often not made very well. And the filler antagonists don't look good against the backdrop of the canonical ones. In Wakfu, the filler episodes also don't shine, presenting the same couple of dull gags. A couple of dull gags and references to the original game. Yes, there is at least some character development here, but it is clearly not the strongest side of the series. In fact, only Nox stands out positively among the characters, as he is inextricably linked to the main plot. However, battle scenes, another strong side of the series, are brought in less often. Instead, you watch for three episodes how the characters play rugby. Not the most interesting way to spend time.
At the same time, there are series with good filler episodes. For example, Gintama is about 80% gags and content that doesn't move the plot forward. Of course, the plot moments are also good there, but people don't watch the series because of that. And the filler episodes added to the anime look quite good and organic. Another good example of a series with filler episodes is Steven Universe. They don't move the plot forward in any way, but they are fun and interesting to watch. In addition, like the filler episodes from Wakfu, they feature character development. However, the characters in Steven are incomparably better, so it's more interesting to watch.