Why do molecules like methoxyethane, ethoxyethane and so on have lower boiling points than isomeric alcohols?
I think it has something to do with the structure, but I don't exactly know what it is.
Yes, structure is important in this respect. Most importantly, the alcohols are able to form hydrogen bonds among each other, which is not possible for the ethers. Since evaporation always means breaking intermolecular interactions in the liquid phase, any additional stabilizing interaction raises the boiling point.