With respect, seems is the appropriate word.
They are making gains in some areas, and those areas and the areas they hold get hurt, badly. But, if they get driven out of one area (like the Kurds are doing to them, slowly) they'll do a flashy and brutal advance in another to counterbalance the loss, along with some selected videos of executions, maimings, torture, and other warnings to the peasants of what is coming their way.
In an impersonal way, you can almost admire their tactics. They are, without doubt, the first real media army, and they ARE an army, not some bunch of fanatics.