I disagree. I have sewn lightweight leather, straps of various kinds, and similar material on my Wally-World Brother sewing machine. It's a matter of getting the right needle, the right thread, and going slowly while assisting the machine with feeding smoothly. I wouldn't try it for any but the most lightweight leather, although I've sewn some pretty substantial pieces of vinyl, but on the whole, I think people underestimate their sewing machines. Denim--of any weight that I have ever encountered--is absolutely no problem, nor is Cordura, for the typical home machine. Really, leather is the only questionable area you've raised, and just keep it lightweight.
Personally, instead of going nuts trying to obtain and maintain an industrial sewing machine, unless you are planning a lot of heavy duty all-leather pieces, I'd just take any small jobs involving heavier leather to a tailor/shoe repair, and do the rest on a standard home machine.