Nope, he hasn't... even ignoring other storylines completely, with a Cosmic Cube in hand, they could have evacuated everybody to terraformed Mars... and we know that star hasn't committed suicide, now don't we?
Plus it's not like he wasn't the one having Black Swan say it could work in the first place.
It's not readers suggesting that they, personally, could have solved it... it's readers saying, well, if Reed just pulled this trick that he in fact succeeded with in story X, why wouldn't that work? And therefore wanting to be shown why that option, which the character should remember having worked, wouldn't this time.
Which, if this is meant to be the same Reed Richards, T'Challa, Tony, etc., I think is a fair point to make.
And then there are the new solutions that occur to readers based solely on what Hickman has set up in this storyline... and if they occur to readers, then if these characters are supposed to be such geniuses, they couldn't have missed them. There may be reasons for those to fail as well, of course, but the writer ignoring them doesn't show us that.
Well, yeah... it certainly showed us that evacuation of at least the mutants from an Earth about to be destroyed was perfectly possible.
Of course, by that same token, the disappearance of all the Earthless universes in this current story tells us that Remender's Planet X was shortly doomed, anyway, right? Although how did Katie grow up so much in a little more than eight months?