It probably doesn't help that the Kaiser appears in folk memory outside Germany as either a buffoon or villain halfway to Hitler.
Ann, your are comletely correct. 100 years off the throne is one thing, but when it's combined with 100+ years of positioning Wilhelm II as you say, it is nearly impossible to re-brand him or his family's history in a positive way. The Hohenzollerns need the PR firm the Windsors use! Propaganda does work and the Kaiser is unfortunately fully entrenched in a very negative image. Even if how he is positioned were mostly true, it's revealing that after 100 years there is no relaxing of the disdain. Conversely, 100 years after Napoleon's demise, about the time when Wilhelm II was getting in trouble, the villainy of Napoleon had largely been toned down if not forgotten.
Remember that alongside the Napoleonic
leyenda negra in the allied monarchies (UK, Austria, Russia and Prussia / Germany), there was also a heroic Napoleonic cult in the countries that had tasted freedom thanks to Napoleon's reforms and rearrangement of the European map: Italy, Poland, Norway, Finland? and indeed among all the left-wing and anti-establishment elements of all European nations except the UK. The Polish national anthem even says:
Przejdziem Wisłę, przejdziem Wartę,
Będziem Polakami.
Dał nam przykład Bonaparte,
Jak zwyciężać mamy.=
We'll cross the Vistula and the Warta,
We shall be Polish.
Bonaparte has given us the example
Of how we should prevail.
It is of course highly ironic and quite evident for even the most arch-Prussian German nationalist that Napoleon (or his shadow), more than anyone else, shaped the German Empire, with its popular sovereignty disguised as mystic union between princes and tribes, universal male suffrage and presidential emperor / imperial president. Hence Prussian Friedrich Wilhelm IV and Wilhelm I's reluctance to accept the imperial title.
What puts Nicholas II in a positive light today is only the regime that followed his, not the side he fought on in WW1. When one considers the obvious links between the real tsars and the red tsars that followed, it is indeed thought-provoking that the same leeway is not granted to the Hohenzollerns with regard to Hitler and Nazism. The reason might be the Germans' own reluctance to identify with and promote the Hohenzollern emperors, as they have been taught (and relieved?) to put parts of the blame for the Third Reich on the Second Reich. (Compare this to the Austrians' obvious celebration of Franz Joseph.) Germans are often surprised that foreigners can have a positive view of the Kaiser simply as a jolly icon of belle-époque Europe.