Where would AJ, Wilder, and Fury rank if they never fought again?

It's a distinct possibility and even probability with Fury. The other two will fight again, but its still interesting to think where they would rank among HWs all time. People tend to underrate fighters while they are still active, but if you think about them historically, I'd argue all three are top 50 HWs.
AJ: Five successful title fights, perfect record, 100% ko rate, and beat an ATG in one of the best fights of all time. Beat about 4 other top 10-15 hws. He'd edge into my top 25. When you actually go through the hw ATGs, I think he's at least at the same level of the Max Baers of the sport that would be around there.

Fury: Top 35. Only one successful title fight, but beat an ATG and ended a nearly unprecedented title defense span. Unbeaten, and but his resume apart from Wlad isn't quite as impressive as AJs has become, and a spectacular flameout.

Wilder: Top 50. Probably get flack for this, I'm sure people will use this as an opportunity to troll Wilder. But while he certainly deserves criticism, there's no question he's had meaningful and difficult to achieve career success. He's unbeaten and had 7 successful title fights. That's in the top 15 or so all time. Yes, they are vastly weaker title fights than any of the other top 15 hw's in winning title fights, but that's why he's only in the top 50 and not 15. It's still a big feat for legacy despite the poor opposition. Regardless, what he's done is still no mean feat. His opponents have generally still been in the top 15-20. The Chagaevs and Briggs of the world would have been weeded out by now.

Before you rate these guys too low, take a look at historical hws and you can see their accomplishments match up fairly well to where I put them.