I doubt if any of these people ever encountered philosophical theology's modern term "classical theist". The phrase may or may not capture some commonality in the thinking of these individuals (I have doubts about Plotinus). But why must we assume that whatever's common to their thinking uniquely captures God essence, or whatever it is? There still seems to be an implicit demand in all this that we accept a particular brand of theology.
The ideas of God that you're likely going to encounter dealing with actual theists in your life - Christians, Muslims, Jews, Hindus, and some "philosophical/natural theists" - all indeed have in common some points about God, quoting Techne:
1) If God exists, God exists necessarily, in other words, God could not have not existed.
2) If God exists then He has no limitations, God is not limited in perfection, in power, in goodness and in knowledge.
3) If God exists then nothing can come into being or continue to happen without God creating it and sustaining it in existence.
Or, in some other terms: they all believe that God is omniscient, omnipotent, the source/origin of all existence, the Supreme, everything that happen happens under God's supervision ...
I do not believe that these overlaps indicate some higher truth or that they indicate what is essential about God.
Focusing on what actual individual religions have in common and downplaying where they differ may be very misleading; because the things they have in common may bear very different relevance in each of the compared religions, and forcibly focusing on the commonalities can grossly distort the message of each of the compared religions. For example both in Christianity as well as in Hindusim, there is the practice of vegetarianism; but Christianity and Hinduism differ immensely on the importance of vegetarianism.
But why must we assume that whatever's common to their thinking uniquely captures God essence, or whatever it is? There still seems to be an implicit demand in all this that we accept a particular brand of theology.
Not at all. I've been trying to understand how come you repeatedly focus on this demand so much.
That's problematic in my mind. It takes a list of philosophical ideas like necessary being, unboundedness and so on, and then kind of slaps the word "God" onto them.
But isn't 'God' a lot more than that?
Sure.
Isn't God, well... a god? A being worthy of our worship and devotion?
But God can hardly be talked about in that way in the usual interactions between theists and non-theists.
Where does all that religious stuff ccme from? And what justifies us in using the same word "God" to refer to hypothetical philosophical speculations about stuff like necessary or unbounded being, and to Judaism's, Christianity's and Islam's very specific and highly religious content alike? What justifies our somehow equating all of it as one and the same?
Indeed, this equating is a religiological/philosophical/anthropological/culturological abstraction or construct to which the actual individual religions do not subscribe.
Compulsory education on "world religions" tends to lead us to believe that all religions basically teach the same, or have the same goal, or are an expression of the same need or the same truth, but actual individual religions do not think that way (for example, Islam has no tenet according to which Christianity would be equal to Islam, etc.).
So it is questionable to accept the term "world religions" to begin with.
To me, the word "God" looks like a storeroom filled by history's pack-rat, crammed with dusty concepts from many different places and times, that aren't always even consistent with one another.
Indeed, but I do believe it is possible to approach the discussion of the topic "God" more productively.
Again, the notion that all major theistic religions do have some things in common, as mentioned in the beginning of this post, can be used to one's own advantage when feeling pressured by theists.
Namely, the common ideas about God - that God is omniscient, omnipotent, the source/origin of all existence, the Supreme, everything that happen happens under God's supervision - can be used as a quick heuristic against any aversive exclusivism that someone who claims to be a theist may be exerting over oneself.
Instead of getting bogged down by the particularities of Calvinist doctrine, for example, one can quickly restore oneself by reminding oneself of the usual definitions of God (which the Calvinist agrees to as well), and that thus the Calvinist exclusivism is not an actual threat.