During his invasion of the pirate Island, Garp was faced with several Titanic Captains of the Blackbeard Pirates, which also included the former Admiral of the Marines, Kuzan.

Source: https://gamerant.com/one-piece-garp-galaxy-divide-explained/

Following the timeskip, he's now associated with the Blackbeard Pirates, who are likely planning to use Aokiji's Devil Fruit, the Ice-Ice Fruit, for a variety of dastardly plans.

Source: https://www.cbr.com/one-piece-characters-ranked/

More importantly, it was also revealed that the Blackbeard Pirates were now hunting for powerful Devil Fruits.

Source: https://gamerant.com/one-piece-vasco-shot-gabu-gabu-no-mi/

Of course, Garp is also a user of the Color of the Supreme King and he demonstrated its usage recently in when he fought against the Blackbeard Pirates on the Pirate Island.

Source: https://gamerant.com/one-piece-haki-marine-ranked/

Originally, Shiryu didn't have a Devil Fruit, but he received one after the Blackbeard Pirates killed Absalom.

Source: https://gamerant.com/one-piece-strongest-characters-in-hachinosu/

Pizzaro joined the Blackbeard Pirates after surviving an intense brawl inside Impel Down, which suggests that he is a strong individual.

Source: https://gamerant.com/one-piece-strongest-characters-in-hachinosu/

The Blackbeard Pirates are just like real-life pirates, and keeping all their activities in mind, Aokiji could have definitely chosen another crew.

Source: https://gamerant.com/one-piece-aokiji-revolutionary-army/

The focus of One Piece Chapter 1087 was Hachinosu, where the Marines and the Blackbeard Pirates were involved in an enthralling battle.

Source: https://gamerant.com/one-piece-chapter-1087-just-foreshadowed-the-death-of-a-legendary-character/

While Garp's strength is certainly impressive, the Blackbeard Pirates still hold the numerical advantage.

Source: https://gamerant.com/one-piece-marines-blackbeard-pirates-battle/