pyanodons adds very realistic ore processing chains, petrochemical processes (the main developer, pyanodon, is a chemical engineer by trade), energy generation mechanisms, electronics overhauls, and also farming components including both plants and animals.
overall, a full py run will easily take 1500+ hours. it's probably not particularly enjoyable for most vanilla players, but if you liked mods such as space exploration or nullius, you might find some enjoyment in py