IMO your friend's assessment is very correct. Antibiotic resistant bacteria are not going away, and almost nobody has discovered a new 'class' of antibiotics and made that work.
These lysins are probably going to be useful, and not a lot of companies are working on useful alternatives. Several years ago I had a small investment in a now-bankrupt company (AKAO) that had a new antibiotic in the aminoglycoside (think streptomycin-like) class that looked fairly promising in clinical trials as a treatment for hospitalized folks with antibiotic-resistant strains of bacteria.
They also had some pre-clinical 'unconventional' anti-bacterial compounds further down the pipeline, but obviously that work all ended when the company went belly-up. Small company even got it's drug approved, but didn't have the capital to get it to market effectively.
I make a small profit on that one, but not much. And lots of other folks lost a lot.