But then "LDS" is now out of date as well! The leadership has decided that they don't want to be called "LDS" anymore. They even dumped the wonderfully succinct "lds.org" domain for "churchofjesuschrist.org."
Now they want you to use the full name of the Church (at least the first time referenced in the convo), which is "The Church of Jesus Christ of Latter-day Saints." So for example, if you want to refer to a person you would have previously called "Mormon" or "LDS," you should instead use "member of The Church of Jesus Christ of Latter-day Saints." There is a minor relief though. On subsequent references you can shorten it to "Church of Jesus Christ" or "the restored Church of Jesus Christ."[1]
Personally I like the (still silly long) acronym COJCOLDS. But realistically very few Mormons are going to offended if you call them "LDS."
Evangelicals consistently consider the LDS/Mormon faith a danger to their version of Christianity- and therefore seek to label it unchristian to poison the well.
Allowing that counter-messaging to percolate by not embracing their actual name that starts "Church of Jesus Christ," (at the very beginnings was called "Church of Christ," though as you can imagine that led to differentiation issues.[0]) became problematic as the "Mormons aren't Christian" messaging became more and more emphatic from its rivals.
https://www.churchofjesuschrist.org/study/history/topics/nam...
LDS profess Christ, to be sure, and they adhere to OT/NT conservative values, and outwardly seem like nice Christian people. But they also embrace a "new Gospel" with extra books beyond the Christian canon that change the whole message. And, if you pay attention to their terminology while they speak at length, you may eventually realize that the LDS use words that have completely different meanings from the ways other Christians use words. If you've changed the underlying definitions and then speak in the same way, you're saying completely different things to the in-group without outsiders knowing the difference.
The LDS sect is fundamentally "henotheistic" rather than mono- or poly-. They literally believe that Jesus and God the Father are/were separate celestial gods, and they literally believe that every man can become a god of his own celestial kingdom, with a minimum of one celestial wife and celestial children to accompany them for the rest of eternity. They've taken major features of Judaic Temple worship, mixed in a good deal of Freemasonry, and come up with something that is far beyond Christianity as any Christian knows it.
There is, however, nothing incompatible with Christian worship prior to the Nicean creed. Definitely post-Nicean it is a heretical sect vs mainline Christianity, but so is all of non-Catholic/Orthodox Christianity on some point or another if you cite the Catholics as the authority, if only on the issue of who's in charge.
There is plenty in the Bible to support a henotheistic view of Godhood, so it isn't extra-Biblical/Christian, just not the enforced POV post-Nicea.