For now, flatpack and snap sandboxes perf hit are quite significant, and devs don't manage the permissions well so you often end up with software that can't open the files you want.

When you fire and electron app from a sandbox, it's a hog riding a slug, then you try to open your files only to find yourself in a temp folder or chrooted to a config subdir.

It think those tech can bring a lot, but there is still work to do.