Lack of pve content

[Theodric]

There is no such thing as "challenging content", just new.

...but there is, because some content is inherently more difficult to complete and therefore challenging compared to other content. It's also very subjective, so even amongst different groups of players what is considered to be challenging is going to vary across the board. That even applies to a lot of content that is made 'easier' over time through an increase in character power. Some fights will still result in a group wipe if tactics are not adhered to.