MDMA has been in large-scale human trials the longest and is the closest any psychedelic has ever gotten to FDA approval. The FDA isn't going to fast-track psilocybin or ibogaine ahead of MDMA — it takes years of trial data to even get in the queue, and those drugs are further behind.
MDMA is furthest along and remains the bellwether. Agency bandwidth and precedent-setting caution mean nothing leapfrogs it.