Everything in article is excellent point but other big point is schema changes become extremely difficult because you have unknown applications possibly relying on that schema.
It's also at certain point, the database becomes absolutely massive and you will need teams of DBAs care and feeding it.
Everyone tries to plan for a world where they've become one of the hyperscalers. Better to optimize for the much more likely scenarios.
Database is still 40TB with 3200 stored procedures.
Granted, DB size isn't the best metric to be using here in terms of performance, but it's the one you used.
Con: it’s sadly likely that no one on your staff knows a damn thing about how an RDBMS works, and is seemingly incapable of reading documentation, so you’re gonna run into footguns faster. To be fair, this will also happen with isolated DBs, and will then be much more effort to rein in.