If you tried RTMM by itself, with no other add-ons turned on (Or nothing else in your community folder), .. then you should have nothing else except the default sim content and RTMM active? So there should be no clashing. If you didn't run the Default sim + RTMM ONLY, then try it first before proceeding..
But as soon as you mention PINK!! now I think I get why your sim is not working as intended. It's not your add-on content that is corrupt, it's Asobos Official content! I hate to say it but it sounds like some of your Official content has been corrupted.
This can happened at times, with sim updates etc, whereas existing files are attempted to be overwritten while others deleted and so on during updates, whether these updates are visual or hidden, and depending on the streaming condition at the time of an update can determine file quality: IE: a poor condition fed from the download servers can cause corruption.
IE: Two updates ago, I started experiencing pink "people" textures, not only on the ground, but also in aircraft etc and I was a at a loss! Some worked but their jackets and headsets were pink!
I took days to search my own add-on content as well re-downloading liveries for aircraft in an effort to restore missing textures. Well after reading up on it and then contacting an admin on the MSFS official forum, found out it was most likely a result of either missing or corrupt textures in the Asobo Official content and not my own add-on content.
In my case, with PINK people, it was suggested to delete the official content folder
\Official\Onestore\asobo-simobjects-characters
.. and upon restart the sim system scans my official content and will re-download any missing - so I did this and voila a new asobo-simobjects-characters folder/and new files were downloaded upon restart.. and PINK was gone! Fixed.
In your case, sounds like not only people textures but also some of the roof and some building object textures have been corrupted and who knows what else after the last update.
Now I think all of those textures come from files in ...Official\OneStore\fs-base\texture and/or
Official\OneStore\ fs-base-material-lib
So what to do? Well, first turn OFF all of your add-ons. and close down the sim and delete some of the official content folders so the sim can rebuilt them with fresh content!
If you have unlimited internet it would probably be best to re-download all of the official content, if not, then at least some of it, as below, to restore key textures content ... but who knows to what extent the content has been corrupted?
As far as the official content is concerned: at least delete these folders: so that they can restored with new/fresh texture content when you start up the sim:
\Official\OneStore\asobo-simobjects-characters
\Official\OneStore\asobo-modellib-buildings
\Official\OneStore\asobo-modellib-texture
\Official\OneStore\fs-base\texture
Try it and hopefully there is no other corruption in the Official content but again, honestly, to eliminate an problems or corruption in your sim, it would be best to renew all of the official content. (Make sure all other add-ons are off, (Community folder empty).
You could remove all of the official content by deleting the Official\Onestore FOLDER and when you start the sim it will re-download all of the official content.
Or you could re-do the full Sim by uninstalling it then reinstalling.
I know a Pain!! for sure but it sounds like the problem is in your official content and not your add-ons.
Norm