100%, this is all true and something you have to tackle eventually. Companies like this one (Kasava) can get away with it because, well, they likely don't have very many customers and it doesn't really matter. But when you're operating at a scale where you have international customers relying on your SaaS product 24/7, suddenly deploys having a few minutes of downtime matters.
This isn't to say monorepo is bad, though, but they're clearly naive about some things;
> No sync issues. No "wait, which repo has the current pricing?" No deploy coordination across three teams. Just one change, everywhere, instantly.
It's literally impossible to deploy "one change" simultaneously, even with the simplest n-tier architecture. As you mention, a DB schema is a great example. You physically cannot change a database schema and application code at the exact same time. You either have to ensure backwards compatibility or accept that there will be an outage while old application code runs against a new database, or vice-versa. And the latter works exactly up until an incident where your automated DB migration fails due to unexpected data in production, breaking the deployed code and causing a panic as on-call engineers try to determine whether to fix the migration or roll back the application code to fix the site.
To be a lot more cynical; this is clearly an AI-generated blog post by a fly-by-night OpenAI-wrapper company and I suspect they have few paying customers, if any, and they probably won't exist in 12 months. And when you have few paying customers, any engineering paradigm works, because it simply does not matter.