I have large English vocabulary, but when I read: "senescence is
ineluctable," I was stopped.

What is wrong with "old age is inevitable?"

Maybe in Britain or in the Commonwealth countries these words are in common
usage, but I would opt for some a little more approachable and that slides
of the tongue with a bit more ease than either "senescence" and "ineluctable."

If you want to see hyper-polysyllabic translations that are dry and
lifeless, look at Jeffrey Hopkins' (and many of students) translations from
the Tibetan.