The usual criticism of a cinema first date
The standard objection is fair: you cannot talk much during a film. If the entire purpose of the date is to interview each other for two hours, a cinema is a poor room in which to do it.
But that criticism assumes the date is the reason the film was chosen. Costar reverses that.
The film came first
On Costar, both people selected the same real screening as something they could genuinely attend. Only after that overlap exists do they see a profile and decide whether to meet.
That means nobody has agreed to a random rom-com, horror film or three-hour drama just because the other person suggested it. The shared choice already tells you something.
The conversation has somewhere to go
You can meet briefly before the film, then have an obvious conversation afterwards. What worked? What did not? Was the ending earned? Would you watch another film by the director?
That does not guarantee chemistry, and Costar does not claim it does. It simply removes the empty-page problem of a first meeting.
Keep the first meeting simple
Meet at the cinema or another busy public place, tell somebody you trust where you are going, arrange your own travel and keep control of when you leave. A mutual Costar match is an introduction, not a safety guarantee or consent to anything beyond meeting.
If the conversation continues after the credits, great. If not, you still watched the film you both wanted to see.