I would like a sightseeing mode to look at the graphics.

[Harmonea]

Once a dungeon is completed, the Return skill takes you to the final boss room rather than the beginning of the dungeon

Have... you ever actually tried this, because it's completely inaccurate.

The shortcut at the start takes you to the final boss room. Return's functionality never changes, so it's never impossible to access earlier areas. And there aren't any current dungeons that have optional mobs. For older dungeons that do have such mobs, unsynced mode is exactly the "just exploring for graphics" mode that you want.

[Niwashi]

Have... you ever actually tried this

Yes, of course I've tried it, which is how I found out. Up until the final boss dies, the Return skill takes you to the entrance, but once the dungeon is completed and the exit portal appears in in the final boss room, Return takes you there instead. It's possible dying may still give you a chance to resurrect at the entrance, but I don't remember for sure, and if you were alive at the end of the boss fight and there's no more mobs around, that's not an option anyway.

[Harmonea]

Niwashi, please stop spreading misinformation. I use Return in literally every dungeon I run to scavenge for leftover chests after everyone exits.

Return is fine. We don't need devs to devote extra time to some special sightseeing mode. Just use Return.