We have several important contenders, but it is kind of funny that if you rank all contenders by relevance to empiricism, as is rightly demanded by Woit and Hossenfelder, string theory comes out in the lead.

One could argue that this is somewhat due to selection bias, as string theory has been given the most research time/funding historically, thus it's had the longest time to mature. If the other contenders had the same research effort it's very possible that at least one might be found to actually be more relevant to empiricism.

String theory exhibited quantum mechanics plus gravity since the day it was invented, it's not like LQG where setting up three macroscopic dimensions is a nearly insurmountably difficult problem. People think that the problem can be solved, otherwise nobody would bother with it, but string theory is obviously the first and best thing to try.