Is the card disrupting normal play?
This is, admittedly, a rather subjective criterion and is one of the reasons why we've thought long and hard about how we wanted to address Nexus of Fate. This isn't the first time we've taken into consideration the disruption of normal play when it came to determining whether a card warranted a ban: the Eggs deck is probably the most prolific example of this, but we've also seen it play a factor in the more recent bannings of Aetherworks Marvel and Krark-Clan Ironworks. As anyone who's been looped by a Nexus of Fate can attest, the card can easily and significantly disrupt normal play.
The tricky thing with this situation is what makes Nexus of Fate frustrating—a combination of its design and how technology handles the ability to repeat actions. You typically don't run into the same situations in tabletop because our rules do allow for certain shortcuts. When looping a sequence in tabletop, if both players mutually understand what's going on, it's okay to fast forward until the loop is broken—either because the game is won, or the player looping has reached their desired board state. Worst case scenario, players in competitive play can also call over a Judge to keep a stalled game moving. The same cannot be said for digital environments where you must explicitly identify each game choice every time you wish to make it. There's no calling over the games rules engine to explain the situation so you can skip ahead, or to issue a ruling on whether the actions taken could be considered stalling or slow play (at least not yet!). Part of the challenge with these kinds of loops is that even if we manage to win the digital arms race to force a game concede when game states remain unchanged, they could still be disruptive to what we consider normal play. Using Nexus of Fate as an example, win conditions sometimes take a half hour or more to finish, with the majority or all of that time being non-interactive. This said, there are also cases where Nexus sees play and resolves games in a non-disruptive fashion, which is why banning it has been debated for so long.
For now, to reduce play disruptions, we've decided to ban Nexus of Fate in MTG Arena in Arena Standard (best-of-one) formats: Play, Ranked Play, and the Constructed event. We're leaving it unbanned in all Traditional (best-of-three) formats.
Meine aktuellen Paper Decks 
Mono-Green Tron 
Devoted Elves 
Und ich habe Leute gesehen (und es selbst erlebt), die ohne Fountain vs. Burn gewonnen haben, da Standard-Burn sehr kreaturenbasiert ist und man daher mit Removal und eigenen Kreaturen oft schon ewig Zeit kauft.
