Sounds like an ideal scenario, but misses the mark due to the nuances involved in developing a traditional desktop on top of a modern software stack. MATE is still bound by the technology of the time - to run MATE in a modern distro implies that you're running it with the latest libraries available in said distro. And that means MATE has no choice but to evolve to use those libraries (or fork them all to create a brand new distro). Doing it any differently would mean creating a brand new desktop environment (of which there are many to choose from if MATE is not your cup of tea).
MATE's goal is not to run in low-powered hardware, but to provide a traditional desktop metaphor.