Abolitionism was a force with or without Wilberfroce. Would it have taken a bit longer without his vocal support for abolition in parliament? Perhaps, but within a few years of the OTL abolition date, i think slavery would still have been banned
Wilberforce was unique not so much his holier-than-thou attitude, but for his ability to inspire others and work with and get along with reactionaries without compromising his core beliefs, all while battling his life-long poor health. He was very much an Enabler.
A world without Wilberforce would have resulted in a very different and harsher British Empire, and could well have butterflied away the American Civil War.