Completely agree dirt and dust are serious enemies of leather and major factors that lead directly to cracking.
Conditioners that don't penetrate or indeed migrate within the leather exacerbate the situation no end.
Solvents do dry leather, but there is no getting away from the fact that almost all products (a couple claim to be solvent free apparently, but I remain dubious) will contain at least one solvent. Whether you can smell them or not, as several can be odourless, the likelihood is that they will be present.
Some solvents are of course more deleterious than others, such as aromatic hydrocarbons. Then of course there is the universal solvent - water!
Water is certainly not the universal solvent. Water solubilizes polarized organic or mineral molecules. Uncharged (non-polar) molecules such as fats/oils/waxes will not solubilize in water unless a suitable surfactant (soap or detergent - different degrees of the same thing) is added. Surfactants solubilize oils/fats by the formation of mycelles.