The problem IS that they have found nothing. We know the Standard Model, as good as it is, is either incomplete or incorrect and without new physics somewhere we have no indication of how to fix it.
Idk, theres been no major progress since the 60s-70s after QCD, String Theory is a complete dead end and there aren't any great candidate theories out there. So the lack of findings certainly hasn't helped.
This "nothing" is valueable information nonetheless.
Science is just as much (often more) about ruling out hypotheses as it is about confirming them. Sometimes that means ruling out all existing hypotheses, meaning new ones have to be formulated to be tested in turn.
The problem here is that the most favoured hypothesis currently is "there is nothing there that can be discovered with any accelerator that can be built using less than 80% of the world's GDP over the next 50 years." And all the valuable "nothing" we currently find just supports the hypothesis and that there is no point in formulating additional hypotheses.
Lots of Grand Unified Theory candidates become interesting at extremely high energy levels and many of them assume the various fundamental forces will merge. You can test these theories at sufficiently high energy levels.
