As long as you've got some kind of strong sanity checks at I/O boundaries and your language & related library ecosystem's not batshit insane (ahem) it can be fine.
It's when you have JavaScript (not even TypeScipt) sending and receiving JSON (not even bothering with JSON-Schema) to/from Node/Ruby/whatever, saving everything to a permissive document store or to some poorly-normalized RDBMS schema that's missing half the constraints it ought to have and has a few columns that aren't the most correct reasonable type, that you end up with a brittle and slowly-advancing pile of shit pretty reliably. "Let's do a Rails REST API with Mongo and a Javascript SPA & React Native clients!" = run far, far away.
It's when you have JavaScript (not even TypeScipt) sending and receiving JSON (not even bothering with JSON-Schema) to/from Node/Ruby/whatever, saving everything to a permissive document store or to some poorly-normalized RDBMS schema that's missing half the constraints it ought to have and has a few columns that aren't the most correct reasonable type, that you end up with a brittle and slowly-advancing pile of shit pretty reliably. "Let's do a Rails REST API with Mongo and a Javascript SPA & React Native clients!" = run far, far away.