I'm not sure the idea batteries are stagnating is really accurate, especially since some of the material science advancements that would help hydrogen would also help batteries, especially graphene and fullerenes. Having said that, a quick poke around seems to hydrogen storage isn't as stagnated as I'd thought with metal-organic frameworks becoming potential contenders[0]. Not sure that's enough to save hydrogen from the rest of its pitfalls, but it does make things interesting.

[0] https://news.northwestern.edu/stories/2020/04/gas-storage-me...