This is the clearest I can put it: Parties A and B want to enter into an agreement. B will only do so under condition X. Party B is free to state any conditions

This is the clearest I can put it: Parties A and B want to enter into an agreement. B will only do so under condition X. Party B is free to state any conditions they want just as A is free to not accept them. Now substitute "Canada" for A, "Germany"/"France"/"Sweden"/... for B and "Enter a similar agreement with these other 25 countries" for X and you get the current situation. The EU member states decided to make this a condition to all their reciprocal visa agreements. If Canada thinks that's not fair they can withdraw from the reciprocal visa agreements.