The idea that some ancient traditions viewed Yahweh as subordinate to El Elyon (The Most High) is rooted in speculative interpretations of early Hebrew texts. This theory often emerges from a misunderstanding of passages like Deuteronomy 32:8-9, where Yahweh is seen as receiving his inheritance from the Most High. However, within the broader biblical canon, especially in the prophetic and wisdom literature, Yahweh is clearly identified as the Most High God, Creator, and Sovereign of all (see Isaiah 45:5-7, Psalm 83:18).
You site precisely the texts (2nd Isa and some Psalms, Genesis/Ex examples= Redactor's interpolation combining El Shaddai and Yahweh traditions) that identify Yahweh as the Most High, however as you probably know many other texts do not, and many others obfuscate on the point. What you describe as a 'misunderstanding' was apparently a foundational tenet for some that lasted centuries. Yahweh was Israel's God but The Most High was The God of all. Monotheism of 2nd Isaiah never was universally adopted, a compromise was the second power concept reflected in many textual examples:
Ex 23:20 Behold, I send an Angel before thee, to keep thee in the way, and to bring thee into the place which I have prepared.
21 Beware of him, and obey his voice, provoke him not; for he will not pardon your transgressions: for my name is in him.
Even as late as the Clementine Recognitions
For every nation has an angel, to whom God has committed the government of that nation; and when one of these appears, although he be thought and called God by those over whom he presides, yet, being asked, he does not give such testimony to himself. For the Most High God, who alone holds the power of all things, has divided all the nations of the earth into seventy-two parts, and over these he hath appointed angels as princes. But to the one among the archangels who is greatest, was committed the government of those who, before all others, received the worship and knowledge of the Most High God (Rec. 2.42)
And Ascension of Isaiah:
35. And I saw the Lord (Christ) and the second Angel, and they were standing.
36. And the second whom I saw was on he left of my Lord. And I asked: "Who is this?" and he said unto me: "Worship Him, for He is the Angel of the Holy Spirit, who speaketh in thee and the rest of the righteous."...40. And I saw how my Lord and the Angel of the Spirit worshipped, and they both together praised God.
The idea that Yahweh had gone from a son of El who receives Israel to becoming The Great Angel of the Most High in charge of Israel, isn't a difficult leap. Somehow, though appreciating that process of other sons of El becoming recast as angels, I had not seen the potential for the same to have occurred for Yahweh, at least in circles that had not equated Yahweh with The Most High. (like 2nd Isaiah and a redactor of the J and P traditions). There is much more to this.
All of this emphasizes the diversity of theological outlooks preserved in the texts themselves.