I am reading the same book and I am quite aware that the Directory had the final say (and therefore some of the responsibility) but it is clear that the expedition only happened because Bonaparte was an enthusiastic supporter of it. If he had said: too far, too hot, nasty diseases and hostile inhabitants I doubt if they would have asked anyone else to take it on. If the Bonaparte had been willing to direct the same level of effort against Ireland (where none of these things applied) it would have been a far more effective attack on England.
By the way: you said earlier that Egypt was a legitimate target because Turkey was part of the second coalition: I have just checked, and the second coalition was not formed till 1799. Turkey's involvement may have had something to do with the French invasion of its territory.