I presume you're aware this is exactly the Muslim and Jewish criticism of Christianity?
Still, some Jews revere a future Messiah; and recognize the operation of the Holy Spirit in the Old Testament. They will still filter all through One God.
As for Muslims, they (can) critique the Christian God on all kinds of grounds...
...a God of love (vs. the Muslim God of sheer will)
...an immanent God (vs. the purely transcendent Muslim God)
...a highly sovereign God who is interactive with His people (vs. a fatalistic Muslim God)
Bottom line...is that BOTH Muslims & Mormons do not understand a 3-in-1 God. So for Mormons, they reduce God to the level of a man to better understand him. For Muslims, they do the opposite and fail to see the immanence/presence of God...a servant-leader God.