Traditional teaching is the expectation that students will learn because we tell them to.
If I were to create a spectrum of teaching practices from traditional to non-traditional, I think I would use the above as my criteria. Moving away from traditional educational practices has less to do with technology (1:1, iPads, etc) or technique (PBL, PrBL, Challenge based, etc) and more to do with context and motivation. Whenever I assume that the person I am working with will learn because I am telling them, the more traditional I am being.
It isn't so much that "kids learn differently these days" or even that there are boundless opportunities for learning and discovery in our technology-rich world - though both are true and part of the push.
We need to continue moving this direction because learning out of compliance has always yielded superficial understanding for the majority of people and limited the highest levels of achievement to those individuals who were able to find personal meaning and intrinsic motivations despite the system in which they were learning. This is why so many ideas of progressive education don't sound all that new to people who have been teaching for a long time. They aren't.
This misunderstanding may be part of the reason why teachers often feel like they "are not allowed to teach" in PBL. When the distinction is about tools or technique and the ideal is "student learns all by themselves, " many teachers feel like it doesn't allow them to do the very thing that gets them out of bed in the morning and got them into teaching in the first place - helping people understand ideas they care deeply about. PBL teachers absolutely teach and I might argue that a PBL teachers should expect to "teach" a vast majority of the most important concepts in their discipline.
Teaching means helping someone know and understand something they don't know and understand. For me, an ideal learning moment in a PBL classroom would be a teacher responding to sophisticated student questions related to a meaningful concept they were struggling to apply. Now the responses might be a mix of questions and answers, but in that moment, the teacher would absolutely be operating as an expert in their field, leading the students in learning.
The difference is that in good PBL, we create a context where that expertise is needed, valued, and appreciated. Back to the above definition, it isn't valued out of respect or compliance - though of course there will be students who do come with this and it is worth cultivating a culture where individuals respect the expertise of others - it is valued because we have respected students enough to help them come to an understanding of the importance of the problems that make our expertise valuable. And we have helped them come to that understanding BEFORE we have expected them to value our understanding of the answer.