I don't really have a very high opinion of MDMA, it's basically just a modified amphetamine and the amphetamines have a not-so-great historical record, being more likely to lead to addictive behavior. These modified molecules are all amphetamines - just look at the right-hand tail of the molecules in the images and compare to amphetamine.

https://en.wikipedia.org/wiki/Amphetamine

The paper cited on the potential similarity to psilocybin and LSD (which exert their activity through the 5-HT2A receptor) is behind a paywall and mice of course are not humans, so that's very speculative.

However, why mess around with compounds with unknown metabolic breakdown behavior, with unknown side effects and activity in humans, when the existing psychedelics (such as psilocybin, DMT, LSD and mescaline) are fairly well understood in terms of effects on humans?