There's a reason big corporations choose bitcoin as their asset, and rumours of countries talking about bitcoin reserves. That's dominance.
People like to focus mostly on one asset and bitcoin have the characteristics to take the number one position, unlike the altcoins that are very centralized.
Bitcoin dominance is not decreasing and it's an obvious statistics that you can get by looking at both market cap and how much liquidity bitcoin has compared to the entire crypto ecosystem.
Recently since like 2 months ago, bitcoin marketcap decreased from around 66% but it is still above 60.89%. That is still huge and bitcoin remain highly dominant.