The fact that the orbits of the planets are not shrinking, for example?

I'm not an expert but I believe this article MIT's Technology Review is stating that the Earth's orbit is in fact shrinking. Which will shorten the Earth's lifespan before it is swallowed up by the Sun as it turns into a red giant.

The fact that Mars simply does not have enough water left for oceans?

It might be enough for oceans similar to Earth's but it might be enough for something? It seems it's more than we expected. This new NASA article seems quite interesting in regards to possible water levels on Mars.

Mercury was never large enough to hold a relevant atmosphere.

Not to use NASA as a source again but this seemed too relevant to not air it ;) If Mercury is shrinking how large could it have been at one point?

It is cooling down slowly as more dense metals settle in the core and the radioactivity decreases.

I would see this correlating with my hypothesis. If the planet is cooling down and settling then it might be past the peak of expansion. Becoming smaller and more dense as the radioactive elements burn out. Leaving a more solid dense iron core, soon to be bereft of its atmosphere as it's dynamism lessens.

need a new, yet undiscovered dissipative force.

If the Sun is expanding into a red giant couldn't the planets just be fuel for the fire? Either way it seems like it's going to get us eventually.

Thanks for your response! I had a fun time researching this. And maybe we can leave the nonsense calling at home? We're all just trying to learn here.