Saddle soap is pure Glycerin. No lye. You best stuff to renovate old leather is, Neatsfoot Oil, made from boiled cow feet, apply with a brush or sponge Saddle soap is applied damp, not wet enough to sud. Not kidding but cold black tea, which contains tannin is ideal stuf to damp the saddle soap with, just rub in with sponge., or if you want something a bit more modern Nikwax waterproofing leather wax. Vegtable oil will also work. It is boot polish that contains lye, so for every layer of polish on shoes and boots add a layer of saddle soap. Hide Foods are mostly Lanolin, always use gloves with it as Lanolin can cause skin reactions. About 58 years of mesisng about with horses and saddelery.
Surveyor- Leatther is still used for tack, I have one side saddle about 118 years old, still being used, so it's durable if properly looked after. There are Synthetics available, but cheap and nasty, I wouldn't trust my life to them, which you do with tack.