The flashback is nice, though, and ensures it has a home in burn decks that fill the yard (like Neheb, the Eternal and Nekusar)
While Endless Swarm can be a fun Hail-Mary pass in a deck driven by Seshiro the Anointed, Jetmir, Nexus of Revels, or other swarm (Beastmaster Ascension, Collective Blessing) and/or token (Parallel Lives, Annointed Procession, etc.) synergies, everything rides on your army surviving
Most of that overlap comes from giant hatebombs which restrict your opponents options in a way that makes it hard to do anything, let alone remove a jumbo-jet-sized archon
Sure, there are plenty of creatures to be swinging in with, but if youre trying to focus on milling your opponents through radiation counters, youre going to need to make a few upgrades to keep the proliferation up
Add cheap dual lands and utility lands only after the rest of the deck works
You can do other things that combo and control them out of their game