Dany is pretty good at being queen. And she's made it a point to not be like her father recently. She could have just killed Jon Snow... like everyone thought she would. I have zero doubt that Cersei would've killed him.
I really just blame Tyrion for everything that's gone wrong.
Jon wouldn't have strolled over to Cersei and disarmed himself. They're mortal enemies and she's plainly established as the least honorable leader in Westeros. Hundreds of years of political stability went down the drain with Aerys's reign, but his madness wasn't even the impetus for the rebellion, just a great excuse to see it through. Cersei, on the other hand, tries to outdo Aerys's legacy before breakfast every morning at this point. Treating with her would be suicide at best, and handing leverage against the north with two scoops of torture as a hostage if she could even manage to restrain her present all-encompassing murder lust.
He takes this chance with Dany because she's a wild card -- the only one one the board at this point -- and he's operating on the assumption that the world is over if he doesn't secure major support before the Long Night. Dany has a just rep for trying to clean up Slaver's Bay, and should have little motive for roasting him on the spot during a diplomatic call unless she's truly mad; even if she does, the outcome doesn't get any worse. It's a totally sensible calculated risk, and going in person is the best way for him to emphasize the sincerity and grave importance of his mission. If Maester Aemon were alive and healthy enough, he could have had a reputable corroborating witness and Dany's blood relative with him to help with the whole "soooo, there are these ice gods and their zombie servants and they're marching quickly and tirelessly but somehow also very, very slowly south to erase humanity..." but he has no such advantages. Just straight-shooting Davos Speechworth to smooth over Jon's bluntness and obvious preference for redheads.
Right, so we get to the big meet, and Dany "could have" torched Jon Snow, King of the United North, arriving on a peaceful diplomatic call, I guess? Though there would be devastating political ramifications and would become a hell of a hard sell to the Seven Kingdoms afterwards unless she planned to torch the whole continent instead of forging trustworthy alliances, but despite that she still huffs and puffs as though Jon's one insolent word away from being fed to her dragons until Varys's news shifts the power dynamics and forces her to back down. It's not a good look for her, as usual.
She's only a "good queen" compared to some historically abysmal recent examples, and has not demonstrated capable leadership or sound judgment very often; she's just usually rewarded for bad decisions as opposed to everyone else on the show. Dany's little more than a posturing, entitled messianic conqueror reliant on her privilege dragons, her (TV) fire immunity, her thirst entourage (RIP Bold Barry though), and her "freed" slaves (who are not equipped at all, no pun intended, to exercise that alleged freedom, and function no differently; freeing them was for Dany's benefit, not theirs, if it didn't come with viable alternatives to serving her beyond just the words).
She's still supposed to be young, yes (so is Jon), and she's learning on the job, sure (so is Jon), but if she were finally thrust into a position of real Westerosi political power...let's say winning the Iron Throne, after 7 seasons of intense experience and on-the-job training and thoughtful advisory leading up, but minus her dragon "I win" buttons for any otherwise insurmountable roadblocks like back in Essos, and swapping out her brainwashed Unsullied and Dothraki for very different Westerosi liege lords with their own real interests and goals to navigate and power struggles to contend with, and without setting the throne room on fire every week while hanging out inside and selling tickets to the show to affirm her Destined Unburnt Goddess status to everyone around her constantly....where does that leave her exactly?
Stamping her feet about what she Deserves as the Rightful Heir to the Seven Kingdoms and threatening to set people or entire kingdoms on fire if they don't prostrate themselves thoroughly or convincingly enough? As far as optics she's a foreign invader, she's a spoiled brat who has no idea what she's doing and failed upward, and comes at every problem with a compulsive and vapid/implausible/cruel initial plan that's usually countermanded in its entirety by one of her desperately necessary advisers. Then she changes her mind on the spot and does whatever her adviser says instead (even when that's not necessarily a good call either, as per the Casterly Rock junk). Is this supposed to earn her a gold star for Queenship? Lyanna Mormont demonstrated much more about leadership with much less.
It's always important to have good advisers and to listen to their advice. The problem there, too, is that her advisers all drop themselves into her lap on their own, rather than being selected by her, and that she doesn't take their input so much as she completely displaces her own positions in favor of theirs. None of this demonstrates her leadership qualities.
She's been playing on Essos Easy Mode as far as it applies to Westeros and she has no business sitting the Iron Throne. Fortunately she doesn't have the birthright, either. I assume the showrunners will do something stupid, though. ;b