Seeing an uncommonly-played deck break into various Top 8s can be a testament to the deck's strength. Bant Eldrazi has been quietly performing over the last few major modern events, with a Grand Prix Top 8, a MOCS win, and a MOCS Platinum PTQ quarterly Top 8.
Bant Eldrazi thrives against other decks trying to play fair, so you are a favorite against other Modern midrange or control strategies. Not just a bit ahead like many of Modern's matchups, but an immense advantage for the Bant Eldrazi player. These decks, and to some extent players who pilot the fair decks regardless of metagame, will always be a large part of the Modern meta.
Why not just smash every Modern tournament into the ground?
Bant Eldrazi is weak to many of the fast combo decks. Modern has seen a recent influx of quick aggressive creature-based combo strategies, many of them with consistent turn three or four wins. Infect, Suicide Zoo, Dredge, and Affinity have become more prevalent after the banning of Splinter Twin, which previously acted as Modern's combo killer and litmus test. Without Splinter Twin, we see combo decks that are faster and have less interaction. They forego the usual four Serum Visions that are commonly seen in Modern combo decks, replacing consistency with power. This makes these Modern combo decks one-dimensional, and are easier to hate out as a result.
Bant's sideboard is what makes it a viable deck in this meta — it's able to catch up against every deck and cannot be hated out. While these decks are bad for Bant Eldrazi, we can combat them with a carefully constructed sideboard. It's often said that white is the color with the most relevant sideboard options, and Bant has white as well as Ancient Stirrings to "stretch" the sideboard. Notably, Bant doesn't use its graveyard whatsoever, so that gives it even more options.
Since Bant is strong against fair matchups, my strategy moving forward is to Overload the sideboard with hate. By forgoing sideboard slots dedicated to beating "fair mirrors," we end up with a potent albeit narrow sideboard.
With such a polarized sideboard, Bant Eldrazi's combo matchups become closer and sometimes favored. That's all you need to have a top deck, assuming you are dominant over the Jund, Merfolk, Nahiri, etc. mages of the world. The sideboard still needs work, especially in a shifting metagame.
I did end up losing a match against Jeskai where I didn't quite have enough cards to side in. While I don't think one or two more cards would have determined the outcome, it's likely you want another Negate or Stubborn Denial, as they are applicable against control in addition to some combo.
Playing Bant is about maintaining an early mana advantage and snowballing with undercosted threats. I have had some issues with my early game when mana creatures are contested with removal or my hand is disrupted. Some of the older Bant lists ran up to four Tarmogoyf — it could be time to move back to Tarmogoyf to keep up with the speed of current Modern. It would add a bit of consistency in the early game before you get rolling by slimming down the curve.
I'm confident Bant Eldrazi will see a steady increase in play over the next few months even in a hostile metagame. It's consistent, resilient, and straightforward to play. The ability to have a flexible sideboard and a proactive game plan has been an excellent recipe for winning in Modern.