There are other competitors in those niches. Some of which are just indirect ways of storing hydrogen depending how you use it. Ammonia, methane, dimethyl ether, methanol, and longer chain hydrocarbons. All have positive and negative tradeoffs
Similarly there are other competitors for fusion. The difference here is they are orders of magnitude better in most ways. Fission and chemical reactions have much higher power density and vastly lower cost (and fission is already cost prohibitive), renewables are vastly cheaper even with battery or chemical fuel storage. There's not really a good niche for D-T fusion even if we had it today rather than in 50 years.
All the alternatives have serious efficiency penalties. All the alternatives that have carbon atoms in them require either atmospheric CO2 capture (expensive) or capture and storage of CO2 from combustion (and now we're back to storage of a gas, and also we've just increased the per-output-power cost of the system, which is very bad.) Hydrogen is unique in requiring none of that and allowing cheap underground storage.
Similarly there are other competitors for fusion. The difference here is they are orders of magnitude better in most ways. Fission and chemical reactions have much higher power density and vastly lower cost (and fission is already cost prohibitive), renewables are vastly cheaper even with battery or chemical fuel storage. There's not really a good niche for D-T fusion even if we had it today rather than in 50 years.