Jonathan de Blok
Translating native Houdini on the fly into USD will always be a bottle neck. USD in general isn't a performant design, it's made for handling massive Pixar style scenes using cached out animations and instancing techniques.
I think I understand your frustration, but I disagree that it's as big of a problem as you suggest at the moment. I fully transitioned to solaris+karma from redshift and could never go back. IMO you can really mostly ignore most of the USD stuff if you don't want to bother with it, but it can be incredibly handy especially when you are trying to scale up which as you say it's built for.
To me, the main gotcha here, is that at the moment, solaris can't really replace obj, at least for me and many other people I would assume, and a big part of that is due to the translation of native houdini to USD on the fly as you mentioned. I hope and trust that this will change and improve over time, but in the meanwhile, I treat solaris as PURELY an enviornment for doing my lighting, lookdev, and rendering. When it comes to the layout part-- i think most people would agree with me that it's just not there yet, and I wouldn't recommend using it for that.
If you just use obj and then scene import stuff to solaris for lighting etc, it's pretty dreamy. Especially if you end up caching USDs of your scene, which then makes lighting/rendering smooth as butter, and much nicer than working in obj for that. But its super easy for users to get confused about this and end up trying to do it all in solaris, which I think will usually end in regret (for the time being).
There's definitely a lot of UX improvements that can be made to solaris and I know sidefx is very invested in doing this, but it will take some time, and I also want to give them credit that solaris has gotten much much better with important UX improvements that come each release. I'm looking forward to those improvements, as well as optimizations, but in the meantime I do find Karma + solaris to be pretty great for my workflow, and I tend to be working as a solo freelancer or very small studio responsible for all aspects of cg produciton including rendering.