Why does everyone say that MongoDB is not suitable for projects like an online store, etc.?

Question

MongoDB

Why does everyone say that MongoDB is not suitable for projects like an online store, etc.?
They say that monga is not suitable for projects such as an online store or, for example, some kind of system where there are users, some data to which these users are tied by id's. They say that it is difficult to make queries, there are no joins and other pluses that postgreat or regular sql gives.
I'm doing a project on mongo, and I calmly make complex requests, for example, from some kind of filter, it's very simple. You can also use the id's that are in the record in the database to find data in other "tables" and replace the id's in the original table with the found data, which is very convenient.
So, why does everyone say that Monga is the bottom and finally smart? What don't I know?

Answer 1

it seems that you have not reached the transactions ..
and to the fact that you have a product, it has variations, sizes, for example.
and some eccentric took and removed the goods .. and the variations remained. and orders...

Answer 2

I thought so too. And now I have a case where I have 5 million documents in the database. Elementary requests, such as selection by 2 conditions, pagination and sorting take 5 seconds, the CPU flies to 100%, and sometimes everything crashes (I'm still only locally alone, but what will happen after 100 people on the site at the same time). After adding the indexes (which is another hemorrhoid, for each option to do manually) requests are somewhere in 50-100ms, which is also not so hot (I'm used to 10-20ms). And do nothing about it. And the base will grow by 3-4 times. But I'm already considering moving. Monga for small things, where a couple of hundred thousand documents, or if the speed is not important.