What constitutes "filler" and "actual" content depends on each player. Though I'd prefer the distinction of "Content that has something I want" vs. "Content that does not have content I want". For example, Dark Falz Persona was "desired" content for me until the 50th run. After that it became obsolete.

Generally, Sega wants us to spend time online. They have to find ways to entice us to do that without making us burn out or get bored.

For me UH were a great idea, but it would have been massively better if there were Client Orders specifically tailored for them which gave players an incentive to run them beyond waiting for a specific drop. It's similar to the issue with Kuron, Tokyo and Vegas having XH mode when there is virtually no benefit in running them at that difficulty. If we had COs like:
- Kill 90 Natives in UH Naberius for 90k exp from Hans
- Kill <UH boss> from Hans
- Clear <UH area> from Hans
- Kill 90 Darkers of lvl91+ from Revelle
- Kill <UH boss> after breaking <this part> from Lubert
- Kill Infected Enemy of lvl91+ from Lottie
- Kill Luminmech of lvl91+ with JA from Io
- Gather 50x Ultralized Enemy Remains from Kressida
- Deliver <some sort of food that drops from Luminmechs> from Franca
- Some Team Client Order(s) for UH areas
- Some Daily Client Order(s) that have us kill up to 99 of an enemy (or gather up to 99 items) that can only be done in UH
etc, it would make it more interesting since it would feel every time as we're heading to a goal instead of "I just have to run it because there is nothing to do"