I have had two entirely separate dentists tell me to avoid mouthwash, except as something to cleanse the mouth with quickly after a coke or to freshen my breath

I have had two entirely separate dentists tell me to avoid mouthwash, except as something to cleanse the mouth with quickly after a coke or to freshen my breath. The first dentist suggested that it may make plaque worse, but they never gave me an explanation. 5 years later a different dentist told me to avoid mouthwash and instead to 'mouthwash' with the fluoride foam from brushing my teeth, before spitting that foam out and then not rinsing with water.