It's a shame that this out of date/meme stuff continues to give MongoDB a bad rap. It's a great DB if you need to be flexible/move fast and avoid migration headaches (speaking first hand, this has dragged dev cycles quite a bit). Most startups/saas/web apps would benefit greatly from using MongoDB purely from a reduction of complexity standpoint.
The current version of MongoDB, imo, makes you super productive and scales without a ton of thinking. If you're working in Node.js, it's even more useful as the query language works just like a JS/JSON object so writing queries is super fast (compared to SQL where you have to spend a lot of mental cycles figuring out how to map object/array data).
I've found that denormalizing data (not even necessarily copying/duping data, but trying to centralize storage of it) when using MongoDB is the way to get the most value out of it. If you try to treat it like an RDB (which does work but can cause issues with complex queries), you'll run into headaches. If you just design stuff to be nested, though (and use the built-in APIs to query that nested data), it works incredibly well.
The current version of MongoDB, imo, makes you super productive and scales without a ton of thinking. If you're working in Node.js, it's even more useful as the query language works just like a JS/JSON object so writing queries is super fast (compared to SQL where you have to spend a lot of mental cycles figuring out how to map object/array data).
I've found that denormalizing data (not even necessarily copying/duping data, but trying to centralize storage of it) when using MongoDB is the way to get the most value out of it. If you try to treat it like an RDB (which does work but can cause issues with complex queries), you'll run into headaches. If you just design stuff to be nested, though (and use the built-in APIs to query that nested data), it works incredibly well.