This question should be asked to Allah he revealed Sura Maida and then verse 5 in Quran ? There are not ifs and buts in that verse. It is very clear and concise. If you want to make your life difficult go ahead. End of the discussion.
Please highlight what is clear and concise before ending the discussion?
I'm getting these points out of your posts:
1) Food of Christians and Jews is allowed for us to eat even if it's been slaughtered without mentioning the name of Allah, without using the correct technique of zabiha.
2) Every food that we buy from muslims or non muslims should be eaten before saying bissmillah otherwise it'll become haram and sinful.
These are your points, right? Now where is the concept of "zabiha" come from?
According to you we can eat anything allowed by reading bissmillah so there's no need for slaughtering the animal with all the conditions that come with zabiha???