G-d has given Israel permission to be ruled by a king throughout its history (see the books of Deuteronomy and Samuel, for example). The king never ruled in place of G-d but in the name of G-d. The same is true of the Messiah, a human king who will rule over a world of peace with justice for all in the name of G-d, the Almighty King. Similarly, the Torah, holy as it is as the Word of G-d, is not G-d Himself. BTW, the study of Torah will not cease when the Messiah comes, but will increase.
I understand your position. Originally God was to be their King but they rejected God, in favor of a human king, no doubt out of fear of enemy nations who had kings, and God acquiesced:
"But when they said, ‘Give us a king to lead us,’ this displeased Samuel; so he prayed to the LORD. And the LORD told him: 'Listen to all that the people are saying to you;
it is not you they have rejected, but they have rejected me as their king.’" (1 Samuel 8:5-7)
I understand why the chosen nation requested a human king long ago. However, if God is the King when all things are eventually fully restored and renewed (“Behold, I will create new heavens and a new earth.
The former things will not be remembered, nor will they come to mind…Before they call I will answer; while they are still speaking I will hear.” - Isaiah 65) then why the need for a human king? This will be an idyllic time in perpetuity when the LORD will finally be to all an everlasting light and Divine guardian, as per scripture.
Pretty cool OT prophecy:
“See, I will create
new heavens and a new earth.
The former things will not be remembered,
nor will they come to mind.
18 But be glad and rejoice forever
in what I will create,
for I will create Jerusalem to be a delight
and its people a joy.
19 I will rejoice over Jerusalem
and take delight in my people;
the sound of weeping and of crying
will be heard in it no more. 20 “Never again will there be in it
an infant who lives but a few days,
or an old man who does not live out his years;
the one who dies at a hundred
will be thought a mere child;
the one who fails to reach a hundred
will be considered accursed.
21 They will build houses and dwell in them;
they will plant vineyards and eat their fruit.
22 No longer will they build houses and others live in them,
or plant and others eat.
For as the days of a tree,
so will be the days of my people;
my chosen ones will long enjoy
the work of their hands.
23 They will not labor in vain,
nor will they bear children doomed to misfortune;
for they will be a people blessed by the Lord,
they and their descendants with them.
24 Before they call I will answer;
while they are still speaking I will hear.
25 The wolf and the lamb will feed together,
and the lion will eat straw like the ox,
and dust will be the serpent’s food.
They will neither harm nor destroy
on all my holy mountain,”
says the Lord.
“And in the days of those kings the God of heaven will set up a king-
dom which shall never be destroyed, nor shall its sovereignty be
left to another people. It shall break in pieces all these kingdoms
and bring them to an end, and it shall stand for ever; just as you saw
that a stone was cut from a mountain by no human hand, and that
it broke in pieces the iron, the bronze, the clay, the silver, and
the gold. A great God has made known to the king what shall
be hereafter. The dream is certain, and its interpretation sure.”