We have seen several posts recently from people worried that they cannot get hotel reservations in Italy for 2025, because it is Holy Year (or Jubilee year). They say they are all sold out. It seems they are looking at summer 2025— more than a year out. Turns out most hotels do not take rezzies more than a year in advance. So not sold out. Just be patient, folks.
And in any case this is a celebration in Rome. Sure, it will attract a lot of pilgrims, and some of them will take the opportunity to visit other places in Italy. But much of the “over-tourism” in Italian cities like Venice, Florence and other places is driven by factors other than religious purpose.