CRE guy here. A lot of this "productivity loss" is also due to government related staffing issues and bureaucracy. Most people are describing more complex building codes, so I'll add something new.
I had a project that was delayed by over a year during Covid because the city approved incorrect plans, came back and requested revisions, and then lost the physical plans (without us knowing until we checked in asking what the status was). This was almost a year delay and added cost overruns, etc. It also made the required rent higher to recoup those costs and try to be profitable (that deal will lose money). Remember, there's someone at the city working 9-5pm clocking in and out.. they are not impacted if the project is denied, delayed, etc... while the developer is incurring cost of capital of 7-10%.
Another example of bureaucracy: you have to go through a particular order of inspections when developing property. One of them includes elevator inspections. You have to have power before that, so that's another set of inspections.
IIRC, during Covid there were only something like half a dozen elevator inspections for the entire state of CA. The source below says there was 15 in 2019. If your elevator inspection is 2 months late... guess what, your project is going to be late.
https://laist.com/news/elevator-inspections-los-angeles
Remember the modular startup Katerra that gobbled money from Softbank? I knew a developer who did one of their projects. He said Katerra would deliver the units on time, but the city's permitting process was so broken that they couldn't actually install or inspect these units. So they would have to find lots to store the material (+costs & +issues). Katerra's "value-add" was the speed of delivery would cut costs down, but in reality this was hard to achieve "on-site".