If you look at visions and prophecies together, you'll see that they are actually very important in Dany's story. A big part of Dany's personal changes are a result of the 3 betrayals prophecy. While show runners might expect people to believe Danny's later paranoia toward those around her is because of Xaro's acts, it will fall flat for most viewers. Note that they had some visions in HOTU. For non book readers it would have made no difference if those visions were prophetic. Already many of them are wondering about symbolism and prophecy in those visions. A bigger problem is that by downplaying Quaithe and HOTU they are making Dany's story less and less connected to Westeros story. In the books there is a sense of mystery about Targaryan history and possible relation to PTWP, AA and events beyond the wall. Here the best you can say is probably some day dragons will fight White Walkers. There is even less reason to get invested in show Dany's story, because there is absolutely no connection to possible future events in westerns other than she just moving there.
