Why on earth would a government put up barriers to energy independence? Is this because the Polish grid is not stable enough to deal with a substantial fraction of power from renewables or to protect commercial interests?
Specific regulations for on-grid systems in Poland are:
-3,68kW limit for single -phase installations - that's actually a technical limitation.
-10kW limit to receive subsidies for purchase of the system.
-50kW limit for net-billing as a private person, but you'll have to first ensure your connection has the capacity to handle that - it's usually 12kW or less, so you'd need to apply for an increase, which will go through depending on the infrastructure in your area.
Overall large PV farms in Poland lately went through series of temporary downtime in situations where the grid went above the safety threshold of 253V, but prosumers were largely unaffected by this.
Everyone is in on it because panels are cheap and electricity has become expensive, so the investment pays itself off in a few years - especially when you go over the subsidised limit of 2600kWh annually per household with children. My sneaky plan with those panels is to remain below that threshold.