I want to be open-minded, but it would be really difficult for me to adjust to calling someone they/them. Further, as they/them implies plural, I find it even more confusing. I’m not saying I wouldn’t do it if asked, but it would be difficult.
But it has a long history.
> Further, as they/them implies plural,
From American Heritage Dictionary 4th Ed. (En-En)
> Usage Note: The use of the third-person plural pronoun they to refer to a singular noun or pronoun is attested as early as 1300, and many admired writers have used they, them, themselves, and their to refer to singular nouns such as one, a person, an individual, and each. W.M. Thackeray, for example, wrote in Vanity Fair in 1848, “A person can't help their birth,” and more recent writers such as George Bernard Shaw and Anne Morrow Lindbergh have also used this construction, in sentences such as “To do a person in means to kill them,” and “When you love someone you do not love them all the time.” The practice is widespread and can be found in such mainstream publications as the Christian Science Monitor, Discover, and the Washington Post. The usage is so common in speech that it generally passes unnoticed.
From Merriam-Webster's Collegiate 11
> They, their, them, themselves: English lacks a common-gender third person singular pronoun that can be used to refer to indefinite pronouns (as everyone, anyone, someone). Writers and speakers have supplied this lack by using the plural pronouns
> and every one to rest themselves betake — Shakespeare
> I would have everybody marry if they can do it properly — Jane Austen
> it is too hideous for anyone in their senses to buy — W. H. Auden
> The plural pronouns have also been put to use as pronouns of indefinite number to refer to singular nouns that stand for many persons
> 'tis meet that some more audience than a mother, since nature makes them partial, should o'erhear the speech — Shakespeare
> a person can't help their birth — W. M. Thackeray
> no man goes to battle to be killed. — But they do get killed — G. B. Shaw
> The use of they, their, them, and themselves as pronouns of indefinite gender and indefinite number is well established in speech and writing, even in literary and formal contexts. This gives you the option of using the plural pronouns where you think they sound best, and of using the singular pronouns (as he, she, he or she, and their inflected forms) where you think they sound best.
So again, I am not opposed to folks choosing pronouns. I am just saying that it is different, difficult, and will take some time for people to adapt.
Neither "they" or "them" are exclusively plural.