I agree that it does suck when you feel you put more work into a dungeon and end up with nothing while somebody else runs off with the loot when they didn’t put nearly as much effort in as you.
Although on the flip-side, nobody told you that you had to be the one to rush. The dungeons in the game were made to be cleared out as a team. Nowadays rushing has become much easier and is made a lot easier by various additions into the game. Just because you rushed the dungeon shouldn’t mean that you are entitled to loot over somebody else. When it comes down to it, everybody has the same odds at getting loot (warranted they do enough damage to qualify for it).
In short, rushing makes dungeons much easier to go through but was never intended in the design of the dungeon. When you rush a dungeon you are taking on the risk that you have a much higher risk of dying and are okay with that. You can always choose to clear to the boss (albeit much slower than rushing). It doesn’t make much sense to reward people for rushing when in the past they have made advancements to limit it (ie. the changes to Oryx Castle).
As long as there is the option to teleport, there will be people who choose to wait around and let others do the work making it to the boss. RNG is a major part of this game and it can be a cruel mistress. Sometimes you luck out and others you don’t.