Electrolyzer and fuel cells are electrochemical systems and are basically batteries themselves. There is no fundamental downside compared to choosing some other electrochemical system. People are just swallowing the FUD and marketing BS of li-ion battery companies. There simply isn't a big enough difference in efficiency for this to matter to begin with, and even then the gap will shrink away to nothing. For instance, for large installations it is already possible to do heat-recapture and use that heat to drive a turbine. We can see 85% efficiency and above pretty much right now. We are going to see more ideas like that and therefore there won't much of any real difference in efficiency.

The other point is that we are not here to just replace fossil fuels with something just as limited and problematic. The goal is to move all of society to something truly sustainable. In fact, if the goal is to replace every single vehicle on Earth with BEVs, then the goal is already a dead one. It would be both absurdly expensive and environmentally damaging to attempt that feat. As a result, we pretty much have to invest in hydrogen eventually anyways. So we might as well do so now, rather than keep spending everything on what is basically a transitional technology.