Jon's plan was the best solution at this point..just be honest
This is the reason why people was dismissive of those leaks initially. Cause the stuff they were saying made no sense to some people. Even the wight dragon rumor people thought was BS (admittedly i thought it was awesome lol). Jon's plan was a rumor months before the show aired, and when it leaked people was like "this can't be real, cause it's stupid. Well...here we are lol. As far as the plan goes, i mean it is what it is. Like someone else said earlier what else was there for Jon to do? Dany can't just invade because of the moral dilemma that's been tied around her neck. A Dilemma Jon and Tyrion put there.
Yes Cersie can't be trusted but, they wouldn't let Daenerys end it sooner by invading King's Landing right away, so now they're stuck with this bleak prospect of having to trust Cersei and hope they can beat the Night's King, with now 2 dragons.