I’m still looking for quotes, but I think it began with some of the earliest PTS translators and their attempts to be “scholars” and try to question the commentaries.
I remember but cannot find the Rhys Davids’ comment describing the Abhidhamma as “The Valley of Dry Bones”. I think it was the Dhammasangani introduction, but I cannot find it.
I also remember reading doubts expressed about the commentary explanation of more than 60 devas being able to fit on a head of a needle. It was somewhere in the Digha Nikaya, maybe even the Mahaparinibbana sutta. I’m sure they would also doubt the size of Sakka’s throne.
I also noticed that ven Bodhi seemed to be less restrained in his comments for the footnotes in the SN and AN, maybe because it was actually his own work whereas MN was a joint venture, mostly an editing task for unfinished work by ven Nyanamoli. You have to understand, that if he complains 15% of the time, it has a profound effect.
Ven Bodhi makes subtle comments in his lectures and writings that cause a negative view of those who compiled, even the suttas themselves. In the maharahulaovada sutta discourse, Ven Bodhi repeatedly states, "I don’t know how they reported this (reading the mind of Ven Rahula), but this is what it means. Video and TimeStamp is here
As @RobertK mentioned, the commentaries and Abhidhamma “spoil” the attainments of those who believe they are attained. It makes Nibbana and jhana more difficult to attain. For instance, Ajahn Brahm is a disseminator of a Dark Jhana and speaks of a mystical beautiful breath. Nevertheless, there is a clear description of what is beautiful and how it relates to jhana concentration as well as anything wholesome. You can see this in my recent video here.
I’m not sure why, but those who read “Clearing The Path” by ven Nyanavira catch some type of mental state that an ajahn chah monk friend of mine called “The Nyanavirus”. Those infected by this are usually young monks who become quite angry at classical theravadans. They believe the Path is simple and now cluttered because of the Abhidhamma and commentaries. Perhaps that is why the book was titled “Clearing The Path.”? Nevertheless, the author who believed he had attained, had a terrible rare sickness that caused him to eventually kill himself.
Ajahn Sujato, will claim that 80% of the commentaries are true. But again, if one complains 20% of the time, it will have a profound effect on people and cause many to “throw the baby out with the bath water.” EBT’ers seem to reject the abhidhamma because they say they are vastly different across sects. However, I knew a couple of people who have actually studied both and they are very similar and vary only in a few points. It is those few points which cause a key doctrinal difference though. Sort of like the late ven Vaharaka and puredhamma saying anicca means “wishlessness” while agreeing with everything else. It is only one word that is different (or maybe a few more). EBT’ers and Ajahn Sujato often focus on the differences and often imply that new wine was poured into old bottles, when the reality is that the Chinese texts they are comparing are missing some points while containing a vast majority of the common points. However these Chinese texts were likely preserved presumably by heritical sects described in the Kathavatthu. Not only that, they were translated from Pali to Sanskrit which was prohibited. After that, it was translated from Sanskrit to Chinese. After that, there was English. Can’t we just be a little doubtful about who perserved it and how many times it was translated? There is a term for this, ironically called “Chinese Whispers”.
Generally speaking, those who “make up their own dhamma” often reject the commentaries and abhidhamma. It ruins “artistic freedom” from interpretations of the suttas which are “general frameworks” to be memorized. I’m not so sure why they are taken to be complete. Even the suttanta folks have to sift through different suttas to give explanations while staying pure to the mula texts. However, each sutta itself was its own lesson or complete discourse. It was the commentaries and abhidhamma that were taught each time, for each sutta (in some general sense).
Another problem is vinaya. The commentary closes many loopholes, especially with money. It makes life difficult for monks. I have had one suttanta monk tell me that as long as they start eating before Solar Noon it is fine. Then they can eat as long as they want until they get up. He is a strict Suttanta monk.
Lastly, Sautrāntika is not new. It is old. There is just another wave passing through, sort of like Ice ages and climate change. It just happens.
One more thing. It is a myth among the Suttanta folks that those who believe in classical Theravada do not read or study the suttas themselves. This is far from the reality as Suttas are always regarded as the “King” of Dhamma. I like to view the commentaries and abhidhamma more like the footnotes on dhamma. If you are familiar with any type of Buddhist or non-Buddhist material you read, you should be able to “guess” what the footnotes contain.