Except for a couple of small moments and helping Rick in The Walking Dead Season 7 midseason finale Aaron has barely been around. He is the reason the group found Alexandria and ended up staying there. But he hasn’t been seen nearly enough in the last couple seasons.
Aaron was one of the first people from Alexandria to get behind Rick’s leadership. He’s been supporting Rick all along and acting as a negotiator for Rick. The people in Alexandria who didn’t trust Rick at first do trust Aaron. And they have listened to Aaron when he told them that Rick was a capable leader.
Aaron does have pretty good skills, although like Daryl we haven’t seen him use them a lot lately. He’s become a part of the group but he’s often hanging on the edges of the group rather being inside it.
There’s not a lot of the original members of Alexandria left. Aaron deserves to be given a bigger role within the group. They will need his fighting skills and his negotiating skills.
Rick still has to convince King Ezekiel and Gregory to support the war against Negan and the Saviors. Rick isn’t a great negotiator. He gives great speeches but that’s not always enough. Aaron could help Rick convince the other communities to join the fight.