Unfortunately, I think you are correct about longer read times discouraging some readers. I think if there was a way to save your place in a longer story that would help (a story bookmark.) If I can’t read the whole story in one sitting, I won’t start it. I know some writer’s break longer stories into multiple parts. But I think that also discourages people for some unknown reason. Maybe modern culture’s miniscule attention span is to blame.
But I do think estimated read times are helpful. Sometimes when I have just a few minutes free, I will read a short 2 or 3 minute story. I tend to bookmark longer ones, which leads to my dilemma. Although I have been chipping away at the list. I usually try to read longer stories at night when things are quiet and I can focus better.