Love how everyone is ignoring the actual Japanese translation on the whole Domain with open barrier thing
The misunderstanding comes from how one considers the concept of barrier(s).
The word "Field(s)" would be most accurate imo.
Regular DE have a closed field of (sure-hit) CT's effects. Their field(s) of efficiency is restricted by a sort of "barrier".
"Barrier-less" DE have an opened field of CT's effects (not limitless, but opened). Their field(s) of efficiency isn't restricted by any kind of barriers.
Both have their advantages and weaknesses.
While one can't get out of a closed domain, one can get out of an opened one.
Though in a domain battle an opened domain will have the advantage as its field of efficiency has no barriers restrictions.
Dunno if clear...