Gear is a fair point, but I don't think arena ranks are a useful metric. I'm on relatively new arena shards, where it's still easy to break into top ranks. My current GA opponent is on an older shard. He ranks around 500 in squad and 200 in fleet, but he has 8 zeta characters compared to my 3. And unlike me, he also has Revan, GMY and CLS. zRevan and zCLS, that is.
He looks like he might be F2P whereas I'm a small dolphin (more of a porpoise really), but he has more than 7 months of playtime on me according to swgoh.gg. There are so many different factors at play that I can see why CG simply uses GP for matchmaking. And as long as fleet is included the way it is now, I'm okay with that. If I can win just one round of out of three, like I did last time, I'm happy.