> Is it so bad to just click to increment the emoji regardless of the color/tone choice made by the first reaction?

This is sort of what I feel like the parent was implying without outright saying it, too. But: that's not how Slack works. If the only reaction is an emoji of skin tone A (let's say its a dark skin toned thumbs up), and I click that dark skin toned thumbs up to also react, Slack adds a thumbs up with the skin tone configured in the user's settings (which I believe defaults to no skin tone), not the skin tone of the initial reaction.

Settings → Messages & media → Default Skin Tone

There's a big difference between "I wish Slack didn't have optional skin colors" vs "I wish Slack didn't have mandatory segregation"