Usyk, Crawford, Janibek, Opetaia, Lomachenko, Tank Davis etc. I am not sure if there has ever been a time in boxing history where you have as many lefties as now. Especially at the top level. Do you think lefties will continue to hold large advantages or do you think right handed fighters will adjust and learn to defeat them?
It just depends if an orthodox fighter feels comfortable fighting a southpaw generally. A guy like Mairis Briedis was an excellent southpaw-killer and feasted on the angles the foot and hand positions an open-stance match-up offered him and his right hand, whereas someone like Murat Gassiev has always looked cumbersome and awkward against southpaws.
It depend of the boxer he will fought but the most good advantage is that they are not many ! You can look how Constantin Bejenaru the Moldovan was a big challenge against the French Arsen Goulamirian who don't like the southpaws boxers..
Southpaws fight orthodox fighters nearly all the time. Orthodox fighters fight southpaws only occasionally. For that reason, southpaws will always have an advantage.
The guy with the better straight comes out on top, unless you've got great countering ability like Marquez on Pacquiao.