You are not a fail.

[Niwashi]

Where is it stated anywhere that the DF is not to be used to speed run? Can you clearly define what I am supposed to use it for? I have not been able to locate that specific set of instructions thus far.

A DF run, just like any other system of putting a party together, is for accomplishing the goals of each of the party members. That's just a basic fact of it being a multi-player game and that's how multi-player games work. You join together to mutually accomplish your goals. If all the members have the same goal, then you can focus exclusively on that one goal. If different members have different goals, then you go through each of them.

The issue with speedrunning is that it's only good for one goal: just getting to the end. If that's the only goal that anyone in the party has, then it's fine. But that sort of uniformity is far more likely to happen in a PF system, where players are choosing that group specifically because of that one goal.

Because DF pulls in random players, it's far more likely to get different people with different goals. If you have one player who just needs to get to the end, another who just wants an item that might drop from the first mini-boss, another who's there for the XP from all the mob kills along the way, another who's there to work on their skills and learn all the mechanics, then you kill all the mobs along the way and kill the first mini-boss and work through all the mechanics as designed and get to the end. At that point, you've met everyone's goals, so have had a successful run.

Of course, if the DF happens to, just by coincidence, put together a group who all share the same goal, then you can focus exclusively on that one goal just as though you'd designed the group that way. Just don't count on such coincidences happening on any regular sort of basis.