I like the PYP. It's not perfect, but it's related to today's world. Before, you would "themes", you would learn about transport, about X / Y / Z, now the so-called "themes" are much wider, much more connected what currently goes on in this world. You don't have to deal with text books that are old by the time they printed them. Your starting point is what you know already, what you can add / find out, etc. and how you can extend and challenge your learning. Every theme has a slightly different angle with a stronger emphasis on e.g. arts, history, science, etc. Apart from the unit (but also integrated) maths, reading and writing are taught. Some things can easily be connected to the unit, others need to be taught separated. The teacher still teaches, but in a different way, it's not like this is what you need to know, and that's it. It's about providing guidelines, information, sources and strategies that children will learn and use to extend their learning and thinking. Just as in the "old" days, some themes appeal more than others to certain children, but that doesn't mean you can get away with not doing it. Every unit has a final summative task that concludes the unit. During the years, the units build up in such a way that it connects to prior learning (the starting point for each unit is often what do we know already, from school, life, experience, etc.). Reading, writing and maths is frequently assessed during regular testing.
Again, it's not perfect, and it definitely depends on how well the school executes it. I still feel some things kids just needs to learn (read / write / maths, e.g. times tables, etc.) which happens as well (during a school week the kids will have sessions of unit, reading, writing, maths, PE, music, ICT, etc.) but compared to the way we used to learn, I think it's an improvement. There is way more you can get out of it, way more to dive into. I was much more limited to the book I used and instructions I got from a teacher.