I'm pretty sure it's not an issue with Aternos because it doesn't change anything on the servers, that could happen you in other hosts, maybe it's related to your server software (Spigot).
We also had vanilla software at one point so that's not it, also I've tried all of these designs on other spigot servers some other freinds had hosted on their pcs and they all worked fine, I've only ever had trouble with villager breeding on aternos, we do have some data packs but those servers had the exact same data packs so that's not an issue, also double checking the wiki they meet all the requirements to breed they just wont. you always claim to not screw with stuff like this and mob spawn rates when its been proven through testing and people's experience something is wrong with aternos specifically