Next on the list after typos for reasons why a story didn’t receive a 5-star review was too many “he said/she saids”. It’s obviously not necessarily to include who said what with every piece of dialog. Again, balance is the key. When it’s a clear “dialog” with one person speaking, then the other, you can go on for a while, as long as it’s reasonably apparent who’s speaking. Nonetheless, an occasional reminder is good, too. If a conversation goes on for a couple of pages, it never hurts to insert either a “s/he said” or perhaps some action, such as a facial expression or gesture, to indicate who’s speaking.
When readers have to go back and figure out who’s speaking, it interrupts the story flow and throws them out of the story, which is something a diligent author should avoid at all costs.