Make sure whatever you color is the subject.
Make sure the edges are good.
Instead of desaturating the rest of the image completely, just mute it. If you do feel a need to desaturate it all, convert to b/w and adjust color channels for a decent b/w image, then add the color layer back in. At least you can always fall back on the b/w image.
Don’t post it in your portfolio.
Not all selective color is horrible… just the vast majority of it. You could refuse, too, saying something like “I want to create images you can enjoy for many years, and selective color is too gimmicky and won’t stand the test of time.”