Although Lewis writes about the use of the vernacular for the Church of England, his insight is helpful for Roman Catholics, too.
As to the words of the service – liturgy in the narrower sense – the question is rather different. If you have a vernacular liturgy, you must have a changing liturgy: otherwise it will finally be vernacular only in name. The ideal of “timeless English” is sheer nonsense. No living language can be timeless. You might as well ask for a motionless river.
I think it would have been best, if it were possible, that necessary change should have occurred gradually and (to most people) imperceptibly; here a little and there a little; one obsolete word replaced in a century – like the gradual change of spelling in successive editions of Shakespeare. from The Joyful Christian