Some lenses don't have smooth/nice bokeh even when wide open.
Yes thatīs true. The aperture geometry is just responsible for the highlight discs but it has nothing to do with the overall quality of the bokeh.
And even if you have a lens with pentagonal or hexagonal aperture shape you can easily avoid showing it by choosing an uniform background without any backlight sources, e.g. the sky or a distant wall. But if you shoot against a tree with the sun gleaming trough all its branches, you will have dozens of them in the bokeh.