Yes the title Yonko is a fucking joke but you know whats worse someone who works under a clown ass Yonko.
Its not easy to become a yonko from shichibukai.
Blackbeard had to.........
(1) recruit the strongest level 6 prisoners in his crew,
(2) kill Whitebeard and steal his devil fruit,
(3) conquer Whitebeard's territory and
(4) destroy Whitbeard remnants
.........to be a yonko from shichibukai
Luffy had to......
(1) invade Big Mom territory and beat his top commanders (which gave him the fake yonko title)
(2) beat the WSC at Wano
(3) awaken the power of Joyboy (its in his new bounty poster) that WG was scared of
......to be a yonko
Law and Kidd, despite bringing down Big Mom, couldnt become yonkos. Kidd even has a WG supernova under his wing.
But Buggy the clown, who had a crew of weaklings (Harjudin was his S-class mercenary) became a yonko when Mihawk joined him. Thats all you need to know.