If you had a preference for dark hair and many dark haired women were going blonde you might be disappointed in a general decrease in women who met your ideal aesthetic. If you aren’t shallow or are shallow but aren’t a beautiful rich Adonis you probably aren’t turning down any dates based on such criteria but mathematically trends which run contra to preference mean a decrease in average fitness according to your own accounting.
Imagine if a huge portion of men were really into boy bands and mullets. The trend would mean that if you selected men based on other more meaningful criteria like financial stability and emotional maturity that you have an increasing chance of a mullet in your future. As critical mullet mass approaches you may feel disappointed at the popularity of the trend.