The reality is at least we have a guy that will defend his title now win or lose and accept any opponent. Hell how many tentitative matchups did he have last night lol.
People act like McGregor hasn't fought guys as replacements at the last second. He has. Multiple times.
In terms of defending the belt, he obviously hasn't, but in reality, the UFC was fine with that. Instead of defending the FW title, he moved up and won the LW title. Instead of defending that belt, he fought Mayweather. All which the UFC was happy to be involved with. At this point, the sport is not about the belts, but about the money.
You also give Khabib credit for defending something he just won. Whether he defends it or not is yet to be seen. And even if he does, whom he defends it against will matter.
UFC further proved the belts are irrelevant by deciding last night that Ferguson's interim belt was no longer valid and that whomever won last night would be the linear champion. They literally took a steaming dump on their own belts. Which they've done over the years just to try and make a marginal PPV main event seem more relevant.
So really, who cares about defending or winning something that the governing body can and will decide isn't universally recognized by some arbitrary criteria whenever they want?
If you ask me, Khabib isn't the champion. He beat a lower ranked stiff, but didn't beat the interim title holder for it. The interim title holder didn't be the actual champion. So the UFC is left with 2 fights to make to actually unify the belts and get back to some form of legitimacy for this title.