It doesn't make you that vulnerable; it's just as fast as opening with Scout Cavalry, and the only downside is that you need to go on gold early (which is a problem if your gold is forward). Against scouts and straight archers, straight eagles is fine.Straight eagles leaves you super vulnerable. Especially if not walled. Best bet is to go man at arms into eagles. Similar variation in the build. Just have to skip horse collar for a bit.
It doesn't make you that vulnerable; it's just as fast as opening with Scout Cavalry, and the only downside is that you need to go on gold early (which is a problem if your gold is forward). Against scouts and straight archers, straight eagles is fine.
Main problem is, Eagles need so much time to train... This is probably the main reason people dont do em in feudal.
Even in Castle you need like 4 Barracks to really get to decent numbers comparable in force against 2 Stable Knights. Thats quite unconfortable..