It's kind of like A/B testing. A blue button isn't wrong, but a green button coverts better.
Language is the same. If your goal is to communicate, the most easily understood choice is best. Some grammatical quirks do nothing to hinder comprehension and don't need to be pointed out (ie - less/fewer). Others are far more toxic.
However, grammatical quirks which don't hinder comprehension still act as signals of status. Using "less" where "fewer" is more correct, or vice versa, will definitely hinder acceptnce of the message by many, regardless of its comprehensibility.
Language is the same. If your goal is to communicate, the most easily understood choice is best. Some grammatical quirks do nothing to hinder comprehension and don't need to be pointed out (ie - less/fewer). Others are far more toxic.