John Gill Commentary Exodus 18:17

"And Moses` father-in-law said unto him, The thing that thou doest is not good." — Exodus 18:17 (ASV)

And Moses's father in law said to him
Having observed what he did, and heard his answer to the question he put to him:

the thing that you are doing is not good ;
not meaning that it was not morally good, or that it was morally evil; for it was certainly a good thing to inquire of the mind and will of God for the people, and to hear and decide matters in controversy between them, and do justice to both parties; but it was not good for the health of Moses; it was not commodious and convenient for him; it was not for his bodily welfare; it was too much for him, as he explains himself in the next verse.