Though the Heroic mechanic was printed on plenty of decent cards, Dawnbringer Charioteers from Journey into Nyx was never going to be another stalwart card in the archetype. It’s a 2/4 with Flying and Lifelink for 2WW, which isn't incredibly exciting. Its Heroic ability is that each time that it’s targeted, you put a +1/+1 counter on it. This is an ability that's appeared on a good number of Heroic creatures, and it's not bad for an uncommon.
Unfortunately, this isn't an uncommon. That's a gold symbol there for the rarity - it's a rare. It was even a featured card in a Journey into Nyx Intro Pack. In Limited, this card was always a decent pick, though. A flier with lifelink for 4 mana is a strong play, especially with how easy Heroic was to build around in the Theros block Limited environment. Having this at uncommon would've made it a format All-Star rather than just an okay rare-draft.
However, a 2/4 for 4 mana simply isn't too fantastic in Constructed, as it doesn't do anything outside of get a bit bigger. Competitive Heroic decks need to conserve their mana and a 4 drop Heroic creature just isn't going to cut it with such underwhelming stats.
From a casual perspective, the Charioteers are a Human Soldier, so it’s playable in a Heroic Soldier deck in Commander if you desperately need one more Heroic creature. But besides that, it's just a bulk rare with no long-term value.