I will give an objective and subjective answer.
Backend as a Service is a set of services, or microservices, if you prefer, that gives you "everything" you need to maintain a solution that interacts with diverse customers, in general you talk a lot about mobile and web, but it is anything that uses web technologies to communicate, so that what you need to develop in backend minimum, that is, you were just what is specific, no need to worry about what virtually every application has to do, no worries about infrastructure, nothing that is a general and known problem.
We can say that it is a Serverless with a more specific activity.
Well roughly speaking it’s like you have a CMS ready for use, where you customize some things. It itself is a framework, but with a slightly different use.
In general it is provided as a API, same as in a framework, but the latter you have the software in your hands and do what you want with it, including put where you want and take care of as you want, already the Baas you just have to use the API, everything is ready for use.
It has nothing very special that does not exist in other ways, it is a cloud with access to the database in a more controlled way, with facilities for content storage, indexing, user management and common interaction with them, exchanges and message routing, integrations, including with social networks and other mass software, notifications, statistics on the use of your service, advertising control and monetization, specific services such as chat and other collaborative means, business rules, and added features that are common to various application types.
It is complicated to make a list of suppliers and list what is good or bad of each one. I will quote just two examples of giants: Azure Mobile and Firebase.
This is a legitimate way for the industry to offer something ready that makes it easier for anyone who is not a programmer or who has difficulty, or who needs something fast. It’s obviously something with a higher cost than if you decided to do it on your own and it’s less flexible. But it can be cheaper if you count all the work to do something specific, if you tell people that you can do it wrong, have security breaches, and have other difficulties. Of course everything can go wrong, Baas is not silver bullet, nothing is.
You have to decide if it is the one that best suits you, which will give the best experience to your users, who are within the financial expectations of who pays the bill.
Related https://answall.com/questions/153205/quais-as-vantagens-e-desvantagem
– MarceloBoni