Mayans vs Celts

I just played a game as Mayans versus celts. I went for archers and he for woad raiders. It went well at first, raiders can’t do much against my archers, but then he added siege and it was just downhill from there. I trained eagles but they melted against his raiders before they even reached the onagers and scorpions and then his onagers took out my archers. When I tried to kill his raiders first he pulled them back and took out my archers out and then his raiders were free to kill my eco and eagles. What other options do I have in this situations? Onagers to kill his onagers? But woad raiders are also strong against siege.