I don't see any single difference to Bitcoin itself from allowing the OP_RETURN to store more data except that if we don't allow it we are more likely to be less utilized now and in the long run and perhaps the world builds on other rails in the decades to come.
Don't we want to be more utilized? People are so selfish about their current node costs or their current transaction costs.
Eventually we need to pay enough fees to secure the network from attack as our security subsidy ends.