Technically google isn't a monorepo, but when I worked there for 7 of the years I worked in google3, which was truly a monorepo, except for Android, and the kernel, and some open source projects... OK, not a monorepo.
But I also think a lot of companies in the same stage as Notion have fallen into the trap of shipping features (namely AI features) ahead of fixing perf bugs
to be fair, the argument that people don't use google while someone is saying they use google while limiting to a specific site is more the point. while reddit's internal search is terrible is not really the point even if a motivator. googs is still being used nullifying whatever the point of the start of this topic was