I don't think there is anything that stops you from using Report Pages - if you are thinking of replacing power point Add in for Anaplan.
When I compared these two a month ago I found that Report Pages are capable of doing everything that PPT add in for Anaplan does. I also realized that the amount of time taken by ppt addins for retrieving data from Anaplan was higher than Report Page.
Honestly, I tried so hard to find anything that might be missing but I couldn't find anything. I think you are good to go. I could see minuses on ppt side and not report side. Here are the cons on ppt side
Like Time taken to refresh power points is on higher side
Changing the underlying source model in ppt is a pain
Creation time of ppt slide is also on a higher side
Converting those ppt into pdfs ( if needed) is another step which is manual in ppts