If it's full then risking developmental issues for your child should probably be a less important to you than risking a highly contagious illness with the complications that entails (complications include death, permanent cognitive, neurological, respiratory and cardiovascular damage).
Ideally every responsible* parent could choose how they want to manage the risk for their child, but that's not always practical. With limited daycare and schooling facilities, there's a strong push to follow the more ~conservative~ (cautious) approaches. And this is at it should be. As they say "Your freedom to swing your arm ends at my face", so to should your freedom to choose the level of risk you are comfortable with be limited by the freedom for others to choose their level of risk.
*A responsible parent considers the welfare of the child first and foremost, not using children as tools to make points or demonstrate a commitment to a particular ideology or to otherwise serve their own interests.