There may be some instances where you choose to purchase a custom bric for easier implementation of certain features or effects, however the core functionality is there already in Blocs without the need of additional paid frameworks or plugins like Stacks simply to use them.
For more advanced uses you can always insert code from third party resources that allows you to build more or less anything using Blocs. Chances are you will never need to do that or buy a custom bric. There are also a growing number of free custom brics at the https://blocs.store/
There is unquestionably a learning curve when switching and the same would be applicable in reverse. I started with Blocs 2 and there were definite periods of frustration, however Blocs 3 is a massive leap forward, whereas I don’t see nearly as much real development in RW beyond what is obtained through paid stacks.
I think there are a lot of RW users who would gladly make the switch, but maybe hold back when they look at the big investment already made in RW that they don’t want to discard. The problem with this logic is that RW can become a bottomless pit of expense once you jump onboard and users enter a mindset of needing a stack for every purpose. From past experience, many of those paid stacks are only used once or never at all.
Coming back to my primary preference for Blocs, I simply find it faster to build a good looking website. Websites are never quite as easy as drag & drop, because there are creative considerations and dare I say it creative blocks, but all things being equal I find Blocs 2-3 times faster and just a nicer place to spend your day.