The problem with sticking to one attunement is preventing you to use a weapon set to its fullest potential. It’s not wrong, but it’s not very optimal and there has yet to be a good argument to WHY you only should use one attunement. Other than it’s an easier gameplay, I cannot come up with any real good argument.
I can make an argument. By constantly cycling attunements you are putting potentially useful skills on cooldown, not to mentioned the attunements themselves. There’s an argument in PVP situations for cycling attunements proactively to keep targets under control, but in a PVE situation the primary concern is going to be maintaining high DPS, which for most builds is going to involve keeping in fire attunement as much as possible.