Sad fact is that most people don’t care about the quality of their coffee (as shown on this thread). I doubt that they feel the same about their bike or their beer – they just don’t know the difference yet.
I think coffee is where wine was 30+ years ago when everyone quite happily drank Blue Nun.
I used to work near a decent coffee shop, never a queue even in rush hour, 40m down the road costa would have a queue out the door and 10 people in to the street, even in winter. What can you do?
You could advise but I bet that they don’t know anything could be better.