So CS should get a job at tooling companies because that's where deep things are done ?

I don’t think it’s nearly that simple. Some teams are product teams, and they operate higher in the stack. Some teams are straight engineering teams, and they operate much lower in the stack. Lower does not always equal more technical though. A product team dealing with incredible scale can still require deep CS knowledge.

My experience is that teams that act as a platform (and I’m using this term very loosely) tend to have lower level problems to solve. Think of AWS teams vs. large companies. A large company might be dealing with high scale; something like 100k+ transactions per second. An AWS team can have many large companies as their customers, so their scale gets ridiculous; much higher than any single company. This can require more traditional CS knowledge.

Some individual engineers love shipping products though — they like writing a LOT of code and getting things out the door. Some engineers like very carefully working on MASSIVE systems, but they end up releasing way less code. Other engineers like working on very low level embedded systems or whatever.

There are a lot of problems to solve, and none of them are necessarily strictly harder than each other. Some people who can support systems at incredible scale simply cannot cope with the speed of back to back product launches, and vice versa. There are tons of types of talent.