Assuming an earth-like planet, but with several billion more years of cooling and settling (and with no moon to create tides). I'm imagining this planet would be geographically and tectonically tedious, with most mountains worn down and the sea levels relatively even across the surface apart from a few flat islands.
My questions: Assuming the sun is still relatively consisted, Is there some reason human(like) beings wouldn't be able to inhabit said planet? As a follow-up--what would the atmosphere and weather look like?