You can also have good civ and bad civs. Some suits your play style, others wont.
On average playing as Ethiopians wont result in a high win rate. Just looking at the data: You are better of picking Goths than picking Ethiopaisn, since the winrate of Goths is higher then the winrate of Ethiopians. But the win curve over time for both civs are completely different. They also fit different play styles.
As Ethiopians you are on a clock and you have to strike fast. That is your main strength in winning the game. As Goths you are most likely behind for the full game and you have to hang on. If you managed to let the game go to post imp, then you will most likely win.
The stats are clear: Based on win rates there isnt really much difference between these two civs, but they play very differently.