From the outside, big organisations have massive resources and access to experts. But inside there is intense competition for those resources and people. The people are expensive and there are many opportunities so you need to justify spending their time, especially in the FAANG impact ecosystems. Despite this pressure people may misallocate their time and it can look weird if you don't hear the justifications but they are really trying hard to spend time on the right things, and they do feel constrained - there are so many rapidly growing areas that need investment, there's actually always a shortage if you think about what could be done.
Using a library versus building internally is a tough trade-off and can have long term consequences. I think everybody is comfortable with the downsides of building. But we sometimes forget the costs of dependencies. My framework is that introducing a new concept whether written internally or through a dependency has a cost. Each class hierarchy, external tool, build system, etc. has a cost and we must weigh this cost against the benefits. Dependency sprawl is expensive especially in languages like Python or JS where libraries break backward compatibility on a frequent basis. I like that Rachel is bringing up the longterm cost of dependencies, they can often be more expensive than just writing a simple function or HTTP call without supporting libraries. Building may be cheaper.
Some people just hate managing systems they can't fix. Other people enjoy the challenge of reverse engineering complex systems and squeezing the best out of them. It is only reasonable to ask for the job expectations to be explained upfront. Rachel's post about onboarding https://rachelbythebay.com/w/2020/05/22/boarded/ goes into this idea in more depth. There's so many differences even in Silicon Valley. Companies should share more honestly what the day to day will be and their appetite for building. This would restrict recruiting funnels upfront but make people happier.
The problem is that inside a company there are many perspectives. The representatives of the build faction may achieve a temporary ascendancy and will obviously try to hire then and paint a rosy picture, but then the buy faction will see the hires and become highly incentivised to point out the lack of immediate results and trammel scope, causing the conflict Rachel is writing about.