Ethanol is indeed a touchy subject - it seems that most everybody has a theory about how terrible it is, based on some fact that may or may not be relevant to engine operation.
What IS a well-established fact is that gasoline (whether ethanol or not) that sits in a carburetor for weeks or months will slowly evaporate and leave a residue that clogs the tiny passages in a carb. Sometimes a shot of carb cleaner is sufficient to clean it out, but more often it requires removal and dissassembly and a thorough soaking/cleaning. That is time consuming and expensive at todays shop labor rates, and still may not be successful if something was damaged or the solvent did not do its magic the first time. For that reason, most techs would rather replace the carb and know it will work, avoiding a dissatisfied customer and a "do over" repair they probably cannot charge for. For that reason, carb cleaning and rebuild is a disappearing service, done mostly in back yards and country shops. I've become rather expert in removing and cleaning the twin carbs on the outboard engine of my bass boat, which doesn't get used very much.