It's obviously possible to buy gold in non-USD currencies. So I think the gist of your comment applies to the dominance the US has over oil markets. So while the "petrodollar" era is still ongoing but its day seem numbered, e.g. by pushing Russia to seek other export markets besides the West, by the increasingly cool perception of the US by OPEC nations [1], etc.
Not just oil markets- usd dominates gold markets as well. Russia will be selling oil to other countries at a “discount” but to what? The price of oil in usd which is why some counterparties consider the trade. If usd was losing dominance, countries would be offering a premium to purchase oil for something other than usd.
[1] https://www.forbes.com/sites/rrapier/2022/10/05/opec-thumbs-...