To be frank, most critics of SCP as a writing site know neither jack or shit of what is actually going on in there.
Yes, there has been a long-standing desire to "sanitize" specifically two articles; SCP-166 and SCP-231, both of which include or imply underage rape as a major component. Whether the "sanitized" instances are better, I don't know, but I certainly prefer them to using child rape for shock horror. Fixing them is entirely justified.
That being said, "popular" old articles have been removed all the time because they were dogshit and were downvoted for being dogshit until they hit the deletion range. Some of those get rewritten (4715 is an example of an old article rewritten) to comply with modern standards which, to an outside eye, are indeed rather homogenous, but this is not an intentional process.
All of the fearmongering that SCP is "destroying its own legacy" by making everything a reality bender, self insert, fetish, apollyon article, world ender, meta, etc etc whatever is literally just hearsay. No one that says this is actually an active reader. "I read a few articles every once in a while" is not a good sample size to determine anything that happens to a community the size and the speed of SCP.