My reason for disliking fates is the huge amount of content that is put behind them. Be it stuff like events (Yokai and normals ones), relic weapons and more. If you are playing this game for a long time this will just get boring fast, especially since fates are mostly just zerg content. The monsters are mostly not interesting without any real mechanics. So you stand there for hours killing the same thing again and again without any real threat to you. Thats why I like fates like Odin, Behemoth, coerl queen and more. They at least have mechanics and people need to pay attention to them.
You know the game rift is full with rifts, that are kinda like fates. But damn are the nightmare rifts nice. These special rifts are kinda unending and get more and more difficult the more rounds you beat with people. You have random boss spawns that have different attacks and you have rounds where you need to do other things than fighting. Yes even those rifts might get boring after time but honestly they were already more fun the first time I did them than Fates. The highest I had till now were 400 rounds in one rift, where we ran out of time to beat them fast enough and they kinda killed us a lot too. Still if all of this was the content it would get boring too which is imo the problem with fates. They are used a lot and even new content like Diadem where kinda like fates..while the only interesting parts where the bigger monsters that could kill lots of people but sadly they did not happen that often.