Drupal definitely allows you to get 95% of the most common features done very quickly with contributed modules but the assessment that it shatters if you try to bend it too far is very accurate.
Also, the RESTful API is not fun to work with, mainly because the documentation for it is really lacking. It gives you all the information that you need to do CRUD on standard fields but if you throw date or file fields into the mix, you'll be tearing your hair out. It's also quite clunky and tedious to parse responses from since it responds with entire nodes which can include unnecessary RDF info or multiple languages along with field values nested 3+ levels deep in arrays.