Beaker wrote: So is that mean, that I can't make an extroot?
Sorry, I never make or need extroot, so I have no idea.
I believe you are trying to use your USB flash drive as the root storage drive? I only know this is a complicated process and not something for ordinary people to play, I would rather use a router with larger ROM than trying to make this work.
In practice, the uninstall probably might work but it will merely mark that package as unavailable rather than being actually deleted.
If you must uninstall that package, try gpkg, this is the replacement for opkg which is probably what is inside your ROM. Maybe opkg is not installed in your ROM, that's why it didn't work.