Thanks for the great question!
In fact, Haketav Vehakabalah and many others here (link) point to the issue of the pillar of cloud/fire, and therefore explain that וְהָיִ֥יתָ לָּ֖נוּ לְעֵינָֽיִם differently. Many mefarshim interpret it in the past tense, pointing to Yitro's helping of Moshe set up judges. However, Haketav Vehakabalah himself suggests that Moshe instructed Yitro to leave and act as a pair of eyes. According to his understanding, this verse means something along the lines of: since you have seen all of the wonders in the desert, you should go and tell others about what you saw (therefore, acting as a mobile "pair of eyes").
With rare exceptions, those who interpret this as speaking in the future tense understand it to refer to the details of camping, not that he will tell them where to go (see Shadal). Others (Ralbag) say that he said this to be nice, but not that it was truly necessary. Others (R' Bachya/Bechayei) explain that he said this to reassure those who had weak faith.
There are many more answers, but these are some of the main considerations.