The Tsars actually had more success with pan-Slavism since they were helping the Bulgarians, for example, to throw the Turks out. But the Soviet occupation and time have erased just about all of that gratitude. The Poles on the other hand have detested the Russians as murderous boors since the 18th century.
“The Tsars actually had more success with pan-Slavism...”
Yes; and that’s a major reason why Russia entered WWI: it’s ties with Serbia.