your mistake is that you are using market cap ratio and calling it dominance. it is like picking up an apple and calling it an orange! just because coinmarketcap.com is dumb enough to use the word "dominance" it doesn't mean it is correct. in fact dominance in a market has nothing to do with market cap specially when it comes to cryptocurrencies where 1 coin can create billions of tokens out of thin air and have billions of dollars worth of market cap and have a bigger "ratio". and none of that billions of tokens even have to enter circulation for it to have that market cap.
I see your point, but you're talking about 'market dominance' in a classic meaning, related to measuring companies' market dominance - such is simply not applicable to cryptos (as there's no revenue involved). "Dominance" is also a word on its own and can be freely used. It's pretty obvious and clear to everyone that CMC's version relates to market cap dominance only. I see no problem here.
I also tend to agree with you, I always thought it was pretty clear that the word dominance was just used to describe the coin with highest total market capitalization, according to the metrics found on coinmarketcap.com.
Market dominance is obviously something completely different, but that's a totally different context to begin with.