In terms of Unreal blueprints they may be low syntax but they are not low code - you still need to know software development techniques or you will end up in a pile of garbage very quickly (which you can also do with any other language).
What is required when using Unreal Blueprints is game development domain knowledge, which makes sense for all those tools, doesn't make them less no-code.
To use Houdini effectively, you need to know vfx and a bunch of other domains, just like you need to understand shaders if you're gonna use the shader nodes in Blender.
All of those things can be achieved with coding as well, and that's the difference. One you write code, the other you don't. Both are backed by code, obviously, but it's hidden from the user but usually extensible by code.
