I agree with you. People should not enter DF/DR expecting a speed run. However, Party finder can help both groups. If you wanna do a speedrun, say "This is a speed run" when using the PF. This way, potential members know before even going in that it's a speed-run and you should probably know what to do.
But the Party finder can help first-timers as well. "This is a story run. We watch cutscenes and won't do a speed-run", lets Speedrunners know that they probably shouldn't join that party when they wanna finish ASAP. When you use DR/DR who knows what type of people you'll get. Could be speedrunners, could be first timers, could be a mix of both. Don't automatically assume you'll find 4-7 other speedrunners that think like you when you fire up the DF/DR.