Is uniformitarianism still necessary for studying Earth-like planets?

Hutton's uniformitarianism has been an instrumental concept in establishing Earth sciences as a rigorous discipline. However, ever since Gould's famous paper in 1965, we have been wrestling with whether the concept has largely outlived its scientific relevance. Here, I ask this question in the context of so-called Earth-like exoplanets. I argue that, while Earth serves as a valuable initial reference for modelling rocky exoplanets, adhering too closely to uniformitarian assumptions risks greatly oversimplifying the likely diversity of extraterrestrial environments. Stellar nucleosynthesis and disk evolution introduce significant variations in elemental ratios such as C/O and Mg/Si, giving rise to very different mantle mineralogy than observed on Earth. Geologically, tectonic regimes and the carbonate-silicate cycle exhibited non-uniformitarian behavior even on Earth during its history, implying far greater variability when considering exoplanets. For exo-biology, environmental divergences must meaningfully impact biomechanical scaling and biogeochemical cycling. At the same time, our empirical foundation for extrapolating to model any of the above will largely remain what can be observed or measured on Earth. Therefore, while we must keep Gould's assessment in mind as we work up from the idealised concept of Earth-like planets towards the real and grand diversity of worlds in our galaxy, uniformitarianism is indeed still necessary for studying Earth-like planets.