Starting with Collecting Things in American Comics

With the Collection System, the Host can gain some of the abilities of those it has collected. With a System this overpowered, why can Adolf only collect female members?

Collect Skye, turn the tide, and destroy the Chitauri Mothership;

Collect Polaris, destroy Wakanda, and take the mountain of Vibranium as spoils;

Collect Scarlet Witch, save a parallel universe, shatter the darkness, and become the new Supreme;

Collect Avatars, Transformers, and the Venom Symbiote, bringing the abilities of the entire universe together as one;

After learning how powerful Earth had become, Thanos chose to bring even stronger allies and unleash an even more terrifying war. And that meant one thing:

His death was drawing near.

P.S. 1: He has an ordinary native identity and knows nothing about the plot.

P.S. 2: Primarily set in the Marvel Universe, with other films and TV works included. No DC.