Justice League Cosmic Clash is a movie within DC's Lego universe that has Brainiac and about time travel. It has Brainiac trying to complete his collection of planets, of which brings him into conflict with the Justice League and brings in time travel.
This movie is meant for younger audiences, so obviously it can seem childish at times. It definitely fits the bill for younger audiences, so if you have young kids at home, it is a movie recommended for them.
I find it better than some movies in the DCEU. At times it seems like the Lego universe they're making for young kids makes more sense than the timeline of the DCEU, of which is what tries to appeal to the older audiences.
Overall, I find this movie alright.