I know I said I'd go, but...
The Father is indeed the Father of all, even of the Mizraens, but other deities that they worshiped were not He. He goes by One Name, for certain, and will not let all call His Name to be anything. Would you answer to any and all names? He may have titles, such as Father, Most High, Most Holy, KING of kings, and so on, but His Name is but One, which the Mizraens didn't use.
Since Joseph believed in the Father in Heliopolis, it could mean the Mizraens thought to name the Father those names since they saw the Father was with him(and that is wrong because He already has His Name and there be no translation needed), or it could mean, they thought those names were of gods beside the Father as many thought there was more than He.
That's how I see it.
And why can't He? He can, He has been, and He certainly will remain to everyone who accepts His Way; however, it seems how the Mizraens worked, they didn't go according to how the Father taught the Hebrews, at least, after a time. He by no means rejected any people who accepted His Being, but if they were calling out all kinds of names that's not His, they call upon another and not the Father, so how could He be with them then?