I’ve seen splitting things go bad too. But less often and to a lesser degree of pain than mono dbs - a bad split is much easier to undo than monodb spaghetti.

However I think it’s “thou shall” rules like this blog post that force useless arguments. The reality is it depends, and you should be using your judgement, use the simplest thing (monodb) until it doesn’t work for you, then pursue splitting (or whatever). Just be aware of your problem domain, your likely max scale, and design for splitting the db sooner than you think before you’re stuck in mud.

And if you’re building something new in an already-at-scale company you should perhaps be starting with something like dynamo if it fits your usecase.