“traditionally/halakhically-observant thinkers who have engaged academic approaches in a serious way is the definition of an apikores who doesnt believe in Torah min hashamayim.”
No it is not. Engaging with academic approaches, in the sense of reading their arguments and grappling with them, does not mean that you deny Torah min hashamayim. Occasionally, academics make good arguments or ask good questions. It is their conclusions that are usually problematic, but engaging with them and answering their questions is fine.