I'm the first to criticize the expansion of IZ, but there are many fully commercial buildings that were proposed but never started.
One thing that was abundantly obvious is that there were too many commercial buildings proposed, especially compared to residential which was (and still is) severely needed. The biggest issue is that, for the most part, all types of construction fall under the same rigid zoning laws. If you can only build 200'-300' the stumpy labs were considered the better bet than stumpy residential. I have contended that allowing higher buildings for residential compared to other uses would help steer development in this direction.
I have to give Mayor Wu (who I can't stand) a sliver of credit here, for advancing new zoning laws that allow taller residentials downtown. Of course, it covers a tiny area and is taking years to be implemented, and some of her other policies have had the opposite effects of making construction prohibitively expensive, but this is still a positive step in the right direction. How it will play out is another story, particularly with how few parcels are actually affected.
That's fear mongering. Rent control exists in Los Angeles for years and they are still building residential high rises today and had a significant boom in the 2010s
Boston also had a significant boom, the most significant of its existence, that is only now running its course. On the other hand, LA has some problems, and has still underbuilt (highrises in particular) compared to its overall population which dwarfs Boston's.
I give you Exhibit A of LA's issues, Oceanwide Plaza. 3 residential buildings over 500' right in downtown LA, so close to the finish line yet instead are incomplete and have been totally abandoned since 2019. They're now all covered with graffiti, and still in limbo as of today. This is as embarrassing as it gets for a major American city.
https://en.wikipedia.org/wiki/Oceanwide_Plaza