I don't discount that long-range fires won't be useful, but I don't follow how on one hand, the complexity of a "subsurface kill chain" (which is limited to...the boat?) is a hindrance, but planning a fire mission across tens of thousands of kilometers against moving targets isn't a mention. Even hypersonics still take time to reach their target, and surface ship can cover a lot of distance in that time. That's why I'm still of the opinion that IRBMs/AShMs, while deserving of respect, are not a stand-in for an actual ship (or submarine) present on location. It takes time to go from detection (orbital, aircraft, other sensor) to command, to launcher, to waiting for the munition to get downrange and hoping that the thing you're shooting at is still there. If it isn't, they have to maintain contact, keep up communications with the munition in flight to steer it back on target, etc. That's a lot to juggle and quite challenge even for the U.S., and against an adversary who will be trying to disrupt anything along that path. (Something the U.S. has pointed out to "the carrier is dead" naysayers that they are actively planning.)

Subsonic missiles are in theory (and I do think it's theory) harder to hit than hypersonic, but the killchain there can be far simpler and shorter, and much less able to be disrupted. This is more lethal the closer I can get before launch. Sure, there's 2000km cruise missiles from B21s, but if I have the option to get in to say, 200km, I'm going to take it and give my adversary far less time to detect and respond.

That's the crux of my argument why persistent platforms won't be going away. To be clear, I don't think these long range (I'll call them strategic? theater?) fires don't have their place. Both sides are investing in them. But the need for being "there" remains.

You ask if it's better for Australia to spend money on having medium/long range fires into the IndoPac theater, or a submarine. I'll agree with you in part that a nuclear sub, which would meet their aims to do so, might be out of their financial reach. But considering that those long-range fires require complex targeting and communications (note the killchain above!), that may not be cost effective either. The latter requires some pretty robust aerospace capabilities to detect and track targets that they do not possess and would be exorbitantly expensive to obtain. They can use the U.S.'s capabilities, and many NATO nations do so. But so goes their ability to fight independently then. And I'd argue, it can perform less missions than a submarine can.

At the end of the day, I think Australia is hobbled by the fact that they want to project power that their current budget is going to be at pains to provide. I think nuclear fast-attack might indeed be their best option out of a host of painful options, short of ceding the field.

* Addendum: There's a lot of noise made about hypersonics, and I think they're to some extent overblown. Not irrelevant, but overemphasized. For one, subsonic isn't dead. They can be relatively cheap, have long range, and stealthy. Launched low and flying low, they're hidden by the curvature of the earth. If their launch site can be hidden or hard to pinpoint prior (be it aircraft, mobile site, or submarine) then they can still be very effective. The challenge comes when they're launched from far away. Just because it has a 2000km range or so doesn't mean that's advantageous, as the target can move really far in that intervening time. (This is where submarines are dangerous, because they can potentially bring those fires in much closer without being detected than a surface ship or aircraft can, AI-powered ASW or not.)

So hypersonics are attractive here. Just speed them up! Now that potential radius the target moved is much smaller. But it brings it own challenges. Engineering a vehicle to fly at that speed and at low level and deal with the effects on targeting and communications mach 5+ travel creates is no small feat.

"But hypersonics are used today!" I hear some say. Yes. Anything traveling Mach 5+ is hypersonic. So that Iskander SRBM that the Russians bolt to the underside of a Sukhoi and release from 30k is technically a hypersonic missile. But in reality it's ballistic missile they dropped instead of launching from the ground, using internal guidance to hit a fixed target on the ground. Effective for that role perhaps, but not groundbreaking and certainly not going to hit a ship.

So I think hypersonics are another possible weapon in the quiver, but part of a mix, not a replacement. They bring their own tradeoffs.