Poland CAN into space. This was painstakingly done in Magna Mundi. Remained Catholic, obtained control of the Curia, forced the Church to reform to bring moderate Protestants back in into the fold. However, religious nationalism due to the spread of the reformation and ethnic religious differences within the massive Polish empire cause frequent rebellion against the state.
The ethnic polish people are confined exclusively to a relatively small region around Warsaw. The rest are Eastern slavic, like Russians, Ukrainians, Tartar, And Hungarian. Only a doctrine of humanist tolerance and a bill of rights keeps the 'minorities' mostly happy. The vast majority of rebellion is religiously motivated, brought upon by reformed preachers spreading religious nationalism, primarily in the Hungarian provinces.
Magna Mundi Mod. I suggest you reverse your opinion, and try it out again.