While Julia does not offer semantic guarantees that you can avoid the GC, it;s actually quite possible and easy to write code where you're manually managing all your memory and the GC is never invoked.
> - what about GUI design? Heard some mixed messages about it
There's a lot of promising things happening with Makie.jl, Stipple.jl, Dash.jl, Pluto.jl and others. This space is still a little immature in Julia, but it's progressing fast.