As I understand it, the problem is more fundamental than that.
Antibiotics were originally discovered accidentally, and a lot of subsequent antibiotics were discovered/created by investigating and extending the mechanisms of the original discoveries.
We're now running out of those implications to chase down. To get the "next breakthrough" in antibiotics will require another surprise discovery, or some other fundamental breakthrough in basic biological understanding.
Last I heard, the next breakthrough is expected to be the exploitation of quorum sensing. Tricking the bacteria into thinking there are already more than enough of them so they at least stop reproducing.
Another use of interfering with quorum sensing is keeping bacteria docile, even when they've multiplied to levels where they could be threatening to the host.
Antibiotics were originally discovered accidentally, and a lot of subsequent antibiotics were discovered/created by investigating and extending the mechanisms of the original discoveries.
We're now running out of those implications to chase down. To get the "next breakthrough" in antibiotics will require another surprise discovery, or some other fundamental breakthrough in basic biological understanding.