Moses being qualitatively labeled "a god"; Israel's human judges being qualitatively labeled "a god"; the entire "heavenly host" of beings, angels, or malak, being qualitatively labeled "gods". Figures of wood and stone being labeled "gods". And the differences between false and true being predicated upon the almighty's appointment of those called "a god" or "gods" [true] and man's appointment of those called "a god" or "gods". A singular word was used in cases - elohim [eloah singular]. The Greek equivalent for the Hebrew word is theos.
The meaning of the original Hebrew word is preserved in its paleographic representation; the ox [aleph] for strength, the staff [lamed] for authority and leadership, the little guy with is arms raised [hey] for a wonderous sign at power works and events.
It in itself is not a name, but a title, applied by many to many others, and most importantly, applied to some appointed to a position of such strong leadership and authority, such as Moses, the Israeli human judges, and even his own son, who was to become the Christ, and ruling king by direct appointment - indeed, by the authority granted him directly by Yhwh for rulership, and a kingdom, the one appointed and authorized to make real the resurrection and bring forth Yhwh's intended purpose for the very creation itself - his only begotten son, Jesus, John was aware to qualitatively label him "a god", and further detailed and described the origins of this one selected by Yhwh.
Application of this label, this title, to Jesus no more makes Jesus equal to Yhwh than it made Moses equal to Yhwh when applied to him, nor the judges equal to Yhwh when applied to them, nor the angels, when applied to them.
For in the Hebrew biblical world - there is only one exclusive recognition and exaltation of one source of all power, all authority, and all creativity above all other sources of power, authority, and creativity which are themselves dependent upon that one single source. From that one source, all other things owe their very existence. In my opinion, that it is description of the biblically presented "monotheism".
This definition may not meet the more modern developed definitions which forbid applying a title of elohim or theos to any being other than one being. For me, that is not my concern, because this more modern definition is not reflective of the biblical texts which did apply a title of elohim or theos to many beings, other than the one being.
The ancient biblical world described in the Hebrew and Christian texts was not one where there were no other gods in existence, indeed, there were many. Sufficient enough numbers so that the first directive given by Jehovah in the wilderness was "I am Yhwh your god, who have brought you out of land of Egypt, out of the house of slaves. You must not have any other gods against my face" [or before me].
The directive issued above does not say that you will not believe it inappropriate to apply the title elohim [god] to any other being, for even Yhwh himself does so in Exodus just prior to giving such directive. No, the directive states "You must not have any other gods before me"
He then goes on to state, "because I Yhwh your god am a god exacting exclusive devotion."
No god, no person, no being, no creature, no facsimile of anything at anytime, should ever be exalted before, ahead of, or higher than Yhwh. Not Moses [a god so called by Yhwh]; not the angels/malak/messengers/heavenly host [called gods by Yhwh]; not the human judges [also called gods]; and not even Jesus, his own son [called a god by John].
These things whether titled man, plant, spirit, being, judge, angel, son of God, elohim or theos [a strong leader of authorty] should never be given the recognition and exaltation given exclusively to the only true source of life and existence possible - the only true God upon which all other gods, people, creatures, plants, beings, depend for their very existence. Not only do no gods exists apart from Yhwh, nothing exists apart from Yhwh [biblical cites provided if you are interested - but I suspect you already know of what cites I am speaking of]
In other words, the exclusive recognition and exaltation of the one source of all power, all authority, and all creativity above all other sources of power, authority, and creativity which are themselves dependent upon that one single source. From that one source, all other things owe their very existence.
And within this definition, which runs not inconsistently with the biblical depiction, John's use of theos specifically in a qualitative manner certainly does not oppose the biblical depiction of monotheism and its relationship with Yhwh.
Now, on the other hand, you apparently do have concern about John's use of theos [one of strong authoritative leader]to qualitatively describe Jesus, the Christ.
And from what I have observed, that objection manifests primarily because one's definition of "monotheism" [most likely the modern conception] does not reflect the biblical depiction of "monotheism", and most people are not aware of how the terms elohim and theos are actually used in the biblical texts.
And so they struggle, as indeed those in Nicea struggled, as what to make of Jesus, God's own son.
To avoid a problem which was their own created perception, they chose to "make Jesus God". A few years later, they even added an impersonal, unseen force, which reacts upon other things, and made it God as well. So now there were three - three manifestations of the one. Which quite frankly, places it on level ground with how the Hindu viewed Brahman and his sidekicks. Yet those in Nicea would have been the first to accuse the Hindu of being polytheistic.
And so they now give their exclusive recognition and exaltation, not to the one source of all power, all authority, and all creativity above all other sources of power, authority, and creativity - no indeed, they give recognition and devotion to Yhwh's son, rather than Yhwh, and to an inanimate force [ruach] rather than to Yhwh himself.
In my opinion, they then are in violation of his directive given, "You must not have any other gods before me ...because I Yhwh your god am a god exacting exclusive devotion."