This explains a lot but as people have said, there's ways WWE could work around this. Shorter promos, less talking more vicious beatdowns, letting her in on the writing process so she's more comfortable with what she's saying (She came up w/the promo she cut on Nikki and it was one of her most solid mic performances) or getting her a manager. There's zero reason not to play to her strengths and work around her weaknesses.
Slightly related side note: They really need to reevaluate phasing out managers. A lot of folks on the roster have the in ring talent but struggle on the mic and/or aren't as charismatic and could benefit from having someone who can make up for where they're lacking.