That he won is one of the great achievements. Recall that the mere threat of abolition was likely enough to secure the support of the south for the American Revolt. It really was an impossible challenge, yet no one could argue against the rightness of it all.
What Wilberforce did though was change public opinion with his remarkable picture of the packing of a slave ship. With the public engaged, slave support withered away. Recall that Uncle Tom's Cabin did the same in the USA and triggered the Civil War perhaps a generation sooner.
That slavery is still happening is shameful however much we pretend that it is all gone. Even in the USA, the commercial use of incarcerated prisoners from a grossly inflated pool of inmates screams slavery as well. There is no way that the USA has that many more criminals per capita than anyone else. So the game goes on.
We must end poverty. That is what will finally put this practice down.
Wilberforce was often ridiculed and condemned as a traitorous rabble-rouser. He had reason to fear for his life.