The Battle of Adrianople matters for a few reasons
1 - It started in earnest the practice of settling large groups of barbarians in the Empire and giving them more and more rights/autonomy. As a result, it accelerated the "Barbarianization" of the Roman Army. The fact that the armies that fought at the Frigidus were mostly composed of Gothic foederati shows this.
2 - It lead to the death of Valens, paving the way for Theodosius the Great to take over first the ERE then the entire Empire.
1 - It started in earnest the practice of settling large groups of barbarians in the Empire and giving them more and more rights/autonomy. As a result, it accelerated the "Barbarianization" of the Roman Army. The fact that the armies that fought at the Frigidus were mostly composed of Gothic foederati shows this.
2 - It lead to the death of Valens, paving the way for Theodosius the Great to take over first the ERE then the entire Empire.