I can't recall exactly how far behind they are, but if they're permitted to put aside those constraints (unlikely) it'll still take decades at this point.
Here's a paper published in 2020.
https://www.mdpi.com/2571-6255/3/3/44 Prescribed Burns in California: A Historical Case Study of the Integration of Scientific Research and Policy
It's a complex issue so there's lots of reasons why prescribed burns aren't done more, but they have been done for years, and there are new laws to make it easier. The challenges include: Air Quality Laws, Insurance Liability, Federal control of National Forest, and the high population in the Wildland Urban Interface and large number of houses near areas that need fire control. People do build houses in areas called Devil's Canyon and Black Hill, but at the same time large areas of grass and scrub have burned annually each year in Lake County so burns there obviously don't help.
https://www.latimes.com/california/story/2021-10-07/newsom-s...
Every article seems like a chance to spread misinformation with lazy analysis and conspiracy theories about Jewish Space Lasers, Climate Change Denial, or that controlled burns haven't been part of California fire control for all of living memory.
https://www.usatoday.com/story/news/factcheck/2022/10/28/fac...
That is the total acreage that burned. Mostly wildfires. https://en.wikipedia.org/wiki/List_of_California_wildfires
Apparently, prescribed burns are about 125,000 acres/year: https://ww2.arb.ca.gov/our-work/programs/prescribed-burning/....