Believe it or not the number of tourists visiting Florence now is not much more than a decade ago, and actually the numbers are still slightly below those who were visiting Florence prior to Covid, in spite of the fact that the numbers of visitors to Italy are at the same level or higher than 2019, signaling that many visitors are discovering other parts of Tuscany and Italy and not necessarily concentrating in the usual suspects, like Florence or Rome.
It is not true that the crowds are the same 12 months a year. As you can see in the chart linked below (see the first chart), numbers increase dramatically after April and May, reach the peak in the summer months (while schools are out), to descend again when school starts. By November numbers are very low all the way through March, but as you can see April, May and October are nowhere as bad as the summer months. Obviously if you are only used to the numbers of people visiting the rural Midwest, even January will look crowded in Florence, but you are from the Bay Area, so you are used to seeing more than 10 people at once within 50 feet, so you will be ok.
https://ot.toscanapromozione.it/wp-content/uploads/2024/05/Bollettino-Toscana-2023-_annuale.pdf
Staying in the Oltrarno is an excellent idea. At the Ponte Vecchio, on via De’Guicciardini or Piazza Santo Spirito is probably not significantly different in terms of crowds, but away from those spots, especially in the San Frediano neighborhood (the westernmost in the Oltrarno) you will see no crowds.