I feel everyone here can agree that the intentional mocking of a real person for their intellectual handicap is abhorrible. It is the lowest of the low. And, thank goodness, my friends and I never played that way - even as teens. But, presenting a doltish person with other traits as a fantasy character - I think that is where the community becomes split?
I see from some people is this idea that 'intelligence' is this objective thing and innate to our being rather than a product of traits and behaviours we've learned throughout our lives and what we consider 'intelligence' is a product of our culture and what it values.
Instead of playing a "dolt" play a character who doesn't care about learning facts and doesn't have patience for thinking through problems. Or whatever. Give the character some traits and behaviours. Don't just say 'well this character is stupid, I need to come up with stupid things for them to do and since it is innate to their being there is no growth or learning to be had'.
Another thing is to not just make the character 'stupid' in all aspects. People can be below average at some cognitive tasks while being average, good, or great at others. Let the character have strokes of genius particularly when something interests them.
Intelligence is not a monolith, even though our characters have a score for it. D&D has trained us to see characters, and by extension real people, this way. That's not how it works for real life people.
Here is an anecdote - My mother was terrible at math throughout high school. To the point where she had borderline failing marks in each course. When she went to nursing school she was among the best in the class for all of the math related tasks because it was something she was interested in and could visualize it better when she was actually doing something with it.
Isn't it? Portraying a below average Int score seems to be the primary driver of the conversation.
The thing is, the below average Int score does not actually do what many people envision it does. People greatly exaggerate it and then say 'well my character has to be that way because ability score'.
It means the character has a
slightly worse ability to memorize and recall facts and a
slightly lower cognitive resilience.
Even if it did all the things people attribute to it, it would make for unrealistic 2 dimensional characters made up of harmful stereotypes.
Thankfully it doesn't but it really needs to be renamed. If we're renaming races let's rename these ability scores.