5 minutes? 10 minutes?
So... let's discuss this then.
Seriously - how long does Luke's projection last in TLJ? 20 minutes minimum (remember, his plan is to arrive, check in with Leia, go out and "put on a show" long enough for a large group to realize what he's doing, escape through a complex network of tunnels, and presumably get into the Falcon)? In reality, based on what actually happens, probably 30+ minutes. He even takes the time to have a catch-up chat with Leia. He certainly doesn't seem to be in any hurry - at all - i mean as if he's dying every second while he's doing it.
I know they/you have to keep saying "force projection will kill you in minutes" in order to sell why Luke has to die, but then you think back on Luke casually walking in, sitting down to playfully chat with Leia, his deliberate slow/dramatic walk out, the time needed to draw Kylo down from the ATAT, taking time to talk to and taunt Kylo etc.
If every second counted, why wouldn't he be in a hurry?
It's this combination that makes no sense: "his goal is to stall for time" (which infers deliberately wasting a fair amount of time) over what would have to be close to half an hour, and show him doing non-essential things like taking his time, or chatting - but then turn around and say "every second leads you closer to death, even a very short force projection can kill you, it's like holding yourself underwater"?
And so despite all that, you're arguing that in ANH Ben couldn't have done a SHORT 3 minute force projection to Alderaan simply to inform them of the DS plans and what's happened to Leia? That's garbage. If force projection was possible, Ben WOULD have gone to another room of his hut, and done it immediately. All he's doing is passing on a short, critical message, not taking on an army to "stall for time."
And you're saying that a Jedi Master like Yoda - who seems more steeped in the ways of the force than Luke even in TLJ (Yoda still seems to be his mentor to some degree even in TLJ) could not do a 10 minute force projection (or a couple of shorter projections, resting in between) to Bespin at the beginning of the duel - half the length of time Luke does in TLJ - to help Luke take on Vader, given the ENORMOUS stakes?
"Accomplishing probably Zilch"? More garbage.
And you're also totally ignoring the fact that TLJ now sets up force ghosts
with real-world powers - so WHY couldn't Ben help Luke at Bespin in some way as a force ghost? Based on what Yoda demonstrates in TLJ, Ben could definitely have helped Luke in some way in his battle with Vader - a scenario that's immune to all these bogus, contradictory "rules" about force projection.