If I’d have to provide a short and straight answer I would say: No.
The longer answer is: It depends. By the way, this is an answer that people use when the have at least a minimum knowledge of what they are talking about.
Before debating, let’s define what I understand by a fullstack developer.
A full stack developer is a web developer who can develop the front end, back end and the database of a web application.
If we are talking about a proof of concept application than one person can do it. There is not even the need of a serious testing. If by fullstack developer we understand a javascript developer who uses Node.js for backend, a frontend technology such as Angular and Mongo DB as a database, in addition to sound knowledge of CSS and make it working on all possible screens, then we are talking about something next to impossible.
My retention, or temptation to say no, comes when we are talking about a Java/.NET/python/etc developer that does back-end and she/he needs to handle database issues such as designing and optimizing. That’s already more than enough. It’s pretty difficult to keep up with one all these technologies and concept such as distributed and network issues that you will have to deal with them in a serious commercial application. If in addition to these topics — security, testing, good design and performance you want to handle styling and the frontend technologies then you are entering in the impossible zone. Angular is not a short subject and the versions 2,4,5 appeared one after an other. But there is also React and Vue.js. So keeping up with frontend and backend technologies is impossible from my point of view.
Not to mention that nowadays people that aren’t software developers don’t make the difference between a DBA and a backend developer. Also, they don’t understand what is a frontend developer and what is a designer. So a fullstack developer is supposed to know: database design, backend development, frontend development and designing. Fotoshop? Really? All of these in one man?
Yes, you can be a mediocre developer, being a Jack of all technologies, mastering none, but personally, I don’t want to be mediocre. I don’t even like front end. Yes, I am familiar with Angular, CSS but on the long run I am not your front-end man.
I can understand the need of a fullstack developer. You want to pay less people. You want one man army. But I have an question:
If she/he works alone then why do you need her/him to have experience working on large teams?
Conclusion
For proof of concept web applications, a single person is enough. On a commercial application you will need people with thorough knowledge on front OR back — end side. It doesn’t hurt for a backend developer to have some frontend knowledge and vice versa but you cannot say that you have sound knowledge on both sides and that you are ready to face all the technical issues.