I don't think we disagree on the fundamentals here:

"an Is that entails what one Ought Not to do." is what you noted, which of course logically leaves us with 'what should be' vs 'what should not be'.

I agree that unnecessary suffering 'should not be', my point is that this can only be objectively true if good is objectively what 'should be'. The moral fundamental that 'existence is better than non-existence' is required for us to at any point claim 'X should exist". Because all questions of morality chain down to this fundamental question.

Why should suffering not exist? Because it overall lowers the quality of a living being's life. But why should there be a living being at all? Because its an increased concentration and complexity of existence that produces far outcomes than the material alone. Why should there exist anything at all? Because existence is better than non-existence.

The point of a fundamental is you can get to a point upon which you can build from. It also acts as a floor when working backwards. There comes a point where we have an answer, and there are no more questions. The answer is the reason, the fundamental that logically must be.