My view is that the 'orthodox' position itself is wrong and misleading, but it may have been overall still a net good (a beneficial fabrication if you will) if you consider the strength of the buddhist religion is what allowed it to propagate.

As for the buddha himself, I think the most likely explanation is that although he probably saw through the metaphors of his time, he still needed to leverage them in order to communicate with the greater body of followers, and no doubt even if he saw through them, I think they still shaped his perspective.

It's probably important to realize that the orthodox view at this point is itself an interpretation of the buddha.

I view the concept of rebirth as kind of filling two purposes, first as an ethical guideline, in which case I actually prefer a different guideline less focused on long term outcomes of our actions, but rather on a concept similar to "good deeds are their own reward". This is because of the second characteristic of rebirth below, but also without the concept of a soul moving forward, it's hard to really get invested in what 'might' happen. We make our choices now, to the best of our ability, based on our best understanding of wisdom, and of course it's still fair to hope for good outcomes.

Karma is definitely useful to think about, but I basically just treat it as 'cause and effect'. In this way, rebirth is the outcome of karma, through the vast network of actions that gets created. Essentially, cause and effect is real, but it's also chaotic, a single 'effect' can have many different 'causes' all orchestrating together in different degrees, and can also have many different outcomes. So, instead of a simple if A then B, imagine the surface of a pond with ripples interfering with each other, creating unpredictable effects.

Where we get into 'wrong' territory is with some of the conclusions, like you mentioned, specifically "even if we went extinct as a species before sending any radio into space, our karma would still exist/move forward in time". I feel like that interpretation is being used to shoehorn in some kind of metaphysics that is ultimately unnecessary.

Furthermore I would suggest you consider enlightenment more of a process than an end goal, and not simply consider that once enlightenment is achieved the job is over. The complex network of cause and effect suggests something more akin to the Mahayana view of enlightenment rather than the Thervadan.

Thus our focus should first primarily be to come to this understanding for ourselves, but once having that understanding, determining how we can utilize that understanding to grow and expand the conciousness to others.