I also disagree with such all-ages unequivocal restrictions (though in our MA state I think it was 10 people, and many or most Prot. churches wish they had 50 showing up), but the argument can be that just as the State - in the interest of the safety of the commonwealth - has authority to require building permits in order for places of indoor public (and private) gatherings, so for the same reason it can restrict or forbid occupancy. However, there is not real warrant for disallowing meetings in large places in which couples and families and others can practice social distancing, inside or outside.
What about 1Thes. 5:26? Can the state stop this practice?