Value of bombers like B21 or H20 essentially boils down to this: Can they actually fly deep inside peer enemy airspace, drop stand-in weapons, and get out - without being detected and engaged? If the answer to that is yes 9 out of 10 missions - then they're not worth it. If it's yes for 99 out of 100 missions - then maybe. And that's a very tall order for either US or China. In a sense, China and H20 may have it easier there, as more of their missions might entail bombing various island bases in the Pacific. Where US detection asset network may not be as thick and as capable as China's network against B21 trying to reach Beijing, Chengdu, Wuhan etc.
If such bombers are lost too easily and too often - then they don't make sense. During Linebacker II campaign, 741 B52 bomber sorties were made, and 15 planes were lost. That's two percent loss ratio per sortie - which USAF saw as very worrying and which would be unsustainable in a long term war. Even when US had hundreds of B52s in fleet. With H20 and B21, it's almost assured there will be fewer bombers in either fleet.
I think there are, broadly speaking, two types of combat scenarios, peer/near-peer and curbstomp, and you are applying the cost-benefit calculation of one scenario against the expected loss ratio of the other.
When the US was deciding if Linebacker was worthwhile, they were applying the loss ratio of curbstomp, where there was no serious question of whether the USAF could hit those targets, only at what price it would need to pay in treasure and blood. However, if the war was fought against the USSR directly, then the USAF would have had an entirely different level of acceptable losses.
Similarly, in determining whether or not the H20 is worthwhile, the correct measuring stick is the one of peer/near-peer, where successful prosecution of targets is far from guaranteed; indeed, the boarder outcome of the whole combat mission and even war itself is not a forgone conclusion.
With such high stakes, the cost-benefit analysis is fundamentally different, as it’s not just a question of how much it costs to destroy the target, but rather what price you are prepared to pay to destroy those targets. Indeed, you also need to factor in opportunity costs and broader mission/campaign risks as well, so it’s not just a matter of killing something, but being able to kill it by a certain time and the degree of warning you give the enemy.
For example, in the event of war, high value, high impact assets like long range early warning radars, air defence batteries, offensive cruise missile launchers and airfields will be high priority targets that needs hitting and taken out of action ASAP. Failure to do so by the prerequisite time could easily result in far heavier losses on friendly strike elements and maybe even result in the loss of key assets, battles or even entire campaigns.
The ability of stealth bombers to hit highly defended hard targets with minimal warning time and high probability of success is of paramount importance in this context.
It’s of little use to spam a thousand Shaheds at such targets to wear them down 6-8 business days after they needed to have died.
Now, granted China’s dominance in hypersonics does overlap somewhat and takes a lot of the pressure off the H20 programme, and as such, I would suggest that any slippage in the priority list of the H20 would be down far more to do with China’s hypersonic missile advancements as opposed to thinking H6 missile trucks or drone spamming are good enough direct alternatives.
