Going all in on hydrogen is a bit of a loosely defined notion. Mostly it boils down to dumping lots of money on the table for whomever wants to grab it and creating a few photo opportunities for politicians parroting whatever their sponsors want them to parrot. And as it turns out the fossil fuel industry seems to want to claim most of that.

Looking at the physics, green hydrogen has some applications but what politicians seem to be pitching ranges from delusional to physically challenging. Those pesky laws of thermodynamics get in the way.

So, transporting hydrogen at scale is a problem because even chilled to near absolute zero it's still way less energy dense by volume than liquid LNG. And of course chilling it to those levels is challenging and expensive. It takes up quite a bit more space. As in, you need several ships to move the same amount of energy as a single LNG ship. And of course the way to deal with cold gases heating up is to vent some of it (you boil some off to cool the rest). So, not all of it makes it to the destination. It gets worse. Those ships need fuel. And hydrogen isn't it because of it's volume. You'd need to sacrifice most of the shipping volume to storing the fuel to move it around.

Volumetric density of hydrogen is a problem for transport, shipping, planes, aviation, etc. Moving around enough of it to be interesting would require an order of magnitude more ships, trucks, etc. than we use today for moving around fossil fuels. That's expensive.

And all of that is before you consider that creating hydrogen is inherently more expensive than just using renewable power directly (via batteries).

None of these problems has much wiggle room for scientific breakthroughs. That perpetuum motion machine just doesn't exist. Hydrogen generation is already close to the theoretical maximum in terms of efficiency. There are not going to be any 2x or 3x improvements there. Same for volume. You can't chill it any further than absolute zero. Converting it into other fuels works but is also lossy.

There's a role for green hydrogen. It's replacing the enormous amount of grey hydrogen we generate today for things like fertilizer production. Australia is not going to export hydrogen in meaningful amounts, ever. Nor is anyone else going to be able to scale that to meaningful amounts. It's physically impossible. But they'll likely produce some other things that can be shipped out using green hydrogen. Like fertilizer, steel, etc.