Researchers and funding moved on to sexier things. From a capitalist perspective, it's much better to wait for resistant bacteria than produce yet another antibiotic in a crowded field.
It's starting to pick up again. My money is on a continued battle until we develop nanomachines or wipe ourselves out.
The really challenging thing with antibiotics (as a reply below notes) is that if you create a great new antibiotic, nobody will use it unless they have to.
There is resistance out there, but for most infections, the 40+ year old antibiotics work just fine. It's not like almost every other disease where the best drug gets used first line.
Unless the financial incentives are fixed, it's unlikely there will be enough incentive to do the R&D to create new antibiotics.
The key information they presented was that just because bacteria evolve quickly to modern forms of antibiotics, doesn't mean they don't also reduce to their tolerance to older (in this case, 1000 years older) antibiotic-like medicines that we would dismiss outright because it wasn't created in the modern age. Old medicine was very much trial and error, but it doesn't mean it can't also be effective or worth looking into deeper for ideas.