Collun is a kid, despite being 20 since he is a Giant and they mature 2,5x slower.
Kids are supposed to be "useless" and "cowards" it's normal for their age, there is no need to hate.
Nah, Momo did very well and much better for an 8 year old kid ever since Toki sent him to the future. He especially excelled later in Onigashima when he got past his phobia (which most adults aren't capable of) and stopped the island from falling, and deduced by himself that the borders should not be opened yet which the Five Elders themselves praised as strategic thinking from the current leader of Wano.