There are a lot of things that go against basic Econ 101 that businesses still do anyway because it's right. It sure as hell isn't cheaper for anyone to reduce their impact on the environment, but a lot of companies are still doing it (and often above regulatory standards). The cynic might attribute that to good PR, but I like to believe that people are basically good and want to do the right thing, when you get down to it.
The position I am envisioning is more PR-focused anyways; someone who can interact with fan concerns in a much more immediate and personal manner, which is not something WotC has been very good at, generally (except for rules questions I guess?). Knocking out the back catalog archives can take place over time and in the background.
You still have to manage cost/benefit analysis. The cost to sensitivity read every old product they sell on DMsG has to be less than
1. The projected sales of those products in a reasonable span of time
2. The possible lost revenue they would lose but not doing it
3. The potential loss of good will that could harm the brand in the long term.
4. The potential loss of sales from just stopping all sales again.
Right now, they have addressed the issue in the form of the blanket content warning. To do more, you need to convince them that the added work would offset itself via increased sales OR that that it will protect future sales off more lucrative projects (such as avoiding a boycott). Right now, I don't think adding those kinds of sensitivity readings are going to get people who wouldn't have otherwise bought Orcs of Thar to buy it (on the contrary, you're telling them why they shouldn't) nor is it going to convince a lot of people who weren't already going up buy the Rules Expansion box or the Wildlands module to buy it because they owned up to racism from 30 years ago. Unless a sufficient enough number of people refuse to buy and future D&D products until this is done OR PDF sales dramatically spike after doing it, it's not worth the cost in manpower to do it.
Goodwill only has value if it translates into more sales for the company.
Now I'm not an MBA. I don't know the cost of hiring readers to read the backlog nor am I familiar enough with market trends to know what such a move might do to potential sales. I just know the pdf sales are a fraction of a fraction of WotC's profits, so unless this move increases this fraction significantly or not doing it hurts thier mainline significantly (or can somehow be done at low or no cost) than the warning label is the best we're getting and the worst is they start pulling offending titles or all titles.