Even in composite, those dithering patterns could be pretty spotty depend on the quality of the CRT’s comb filter and the size of the display.
You could always just plug composite into an upscaler if that’s what you’re into… but it feels like a rather expensive way to get a blur going. And given the upscale, you may not see a proper blending of patterns anyway.
To be honest, scanlines (even faux scanlines) actually do a lot to trick your mind into blending together dithered patterns for some reason. When I upgraded my Genesis to RGB, I thought I’d miss the blending of the dithered stuff too, but I never really did.
No matter what you do, there’s always going to be tradeoffs. You can make yourself absolutely nutty if your goal is to get every little detail absolutely perfect in your setup. Dithered patterns is just one of those things that you may need to let go of.