This is a literally millennial old discussion it din’t arise in the coffee room it is known as the “Euthyphro dilemma”
I am not going to spend to long on this , because I think reasonable people can disagree. I will point out a few things that don’t quite fit with your take:
1) Avrhom says “חָלִ֨לָה לְּךָ֜ מֵעֲשֹׂ֣ת ׀ כַּדָּבָ֣ר הַזֶּ֗ה לְהָמִ֤ית צַדִּיק֙ עִם־רָשָׁ֔ע וְהָיָ֥ה כַצַּדִּ֖יק כָּרָשָׁ֑ע חָלִ֣לָה לָּ֔ךְ הֲשֹׁפֵט֙ כָּל־הָאָ֔רֶץ לֹ֥א יַעֲשֶׂ֖ה מִשְׁפָּֽט׃” How does this make sense in your view? There is no good/bad outside of Hashem?
2) Rashi Beresishis on “Mitzvosi” דְּבָרִים שֶׁאִלּוּ לֹא נִכְתְּבוּ רְאוּיִן הֵם לְהִצְטַוּוֹת, כְּגוֹן גֶּזֶל וּשְׁפִיכוּת דָּמִים: Ie if Hasehm did not command us not to steal, we should know not to. How?
I am inclined towards a third option that the two statements are both true ie it is a definition and the question is a false dichotomy. For example is a an object round because it is a circle or a circle because it is round, this is a false dichotomy both are true.
So is an act moral because Hashem commands it or does Hashem command it because it is moral? Both! Sacks discusses this in one of his books
Again, I am not trying to convince you and you can disagree wit al points ive said. I’m just pointing out that it isnt so black and white