Asilean's words weren't only mockery toward Merr. They were also an indication of what Merr needed to improve. At first, it might seem as if Asilean meant that the net of spatial magic moved too slowly, and that was why it was unable to catch Asilean.
But Asilean talked about more than that. It didn't take long until Merr understood what he meant. His way of casting magic wasn't necessarily slow. It was just that he spent too much time thinking about what to do.
Merr's teachers had taught him that in this situation, you use this method to fix it, and in that situation, you use that method to attack your opponent. Of course, since there were several methods and ways that would do the job in every possible situation, Merr first had to assess the situation in as much detail as possible before quickly going through the viable solutions.