Haven't seen the documentary but plan to.
I can only give my sheltered, middle class white boy perspective and won't presume to speak for Indian people or POC more broadly as I am sure their perspectives are totally different.
I watched the show from the start and I love Apu. Beyond the stereotype, he is one of the most upstanding, honest, hard-working and ethical people in the show and also has some of the funniest moments and heartfelt moments in the show's history. It saddens me to think that while I was privileged and sheltered enough to be able to fall in love with the character, that many Indian people were made to feel uncomfortable by the more tangible surface level elements of Apu.
I genuinely believe that in the golden era of the show he evolved from shallow backdrop character into a love letter to first generation Americans who came to the country, grabbed the opportunity with both hands, became beacons of their community and showed up the "real Americans" in the community in terms of real hard work and moral values.
It just also happened that the show was created in a bit of a mini dark age in terms of understanding how racial stereotypes can do widespread harm and as a result some of the choices around Apu's more tangible elements have aged very badly. I just can't accept that he is the creation of racists though and I think it is revisionism to look back and say that. The product of unintended ignorance, yes but not blatant racists. The guy here who made that Klan remark is a tool. The Simpson's was basically as woke as mainstream entertainment got in the 90s. We've just happened to evolve our understandings more since.
Sad situation and there is no real easy way for it to be handled at this point. I can't really reconcile the recent poor efforts of the show to respond to this with the show I once loved, as modern Simpson's literally has no connection in my mind to the classic era. It's just a re-animated corpse being shaken until the pennies stop falling out.