In the sea of new heroes, hero reworks, and changes to team size, the ping mechanic was a new, improved system that seemed to fly under everybody's radar. However, with the cutdown of six teammates to five, it urges more team cooperation and communication. The problem lies in the fact that not everybody has a headset or feels comfortable talking to total strangers. Blizzard realized this was an issue, and gave us a new way of talking to our teammates, without actually using our words.
The ping system was one that was rarely used for the first game, outside of asking for heals, but Blizzard made the new system much more viable and robust. This Reddit video, made by User Refookul, does a great job at demonstrating its new features.
Starting off, you can now ping specific enemies, and let your team know the hero, and their general location by marking them on the HUD. So if a Mercy or a Hanzo is sneaking up behind you, you can now alert your team to their presence, without saying a word. The ping can't track through walls, except for very specific characters like Sombra, and the marker will stop on their last location if they break line of sight, needing to be re-pinged again.
It also adds more tactical pings, where you can basically lay a rough plan of attack with a few simple button taps. Rather than just hope your teammates follow you, a more experienced player can now leave down markers to specify a choke point or alert them to where they're planning to move next.
Overall, it allows a match to be decided more on communication, and basic coordination, rather than if one team has a Discord call, and the others are comprised mainly of randos, who got thrown together in a public lobby.