which sounds similar to working on a large system, doesn't it?

Not really, no. At least nowhere I’ve worked. Currently I work at a company that recently went public and operates near FAANG scale. There are some interesting technical debt issues to overcome and these are challenging. But they’re not arbitrary or capricious. Most importantly they’re not correlated at all with our interview questions, which are designed to select people with recent exposure to mid- and upper-level textbook CS problems. That is, they’re going to naturally select from privileged groups (generally white and wealthy Asians who have attended top-tier universities).