It's not half-assed, it's the whole ass. There are quite a lot of good elements in the story, but they are horribly executed.
Idk man, I've heard lots over the years about people talking about the story "flaws" but alot of that comes down to hating what was done really than standing up on any level of quality.
Stuff like people being mad they have chaos and evil/ order and good kinda of morality. It's a lot of times perspect arguing over pretty overall vague terms or being critical of the greater elements at play over personal philosophy beliefs (which is fine reason not to like it, but calling it flawed is just exaggerating things).
To kinda say my part concise as I can, people get judgy over part 4 morals as if hypocritical actions aren't real. It's like the stupid kinda kinda claims from death note fans that the MC EVADING ARREST AND COMMITING MURDER VIA UNCONVENTIONAL MEANS is somehow lawful evil. You could just as easy call them chaotic good because they are trying to avoid killing "innocent" people in vigilante fashion.
More fair complaints like people pointing out the supports are weaker are true. The game has too much jumping around for supports to work as well as the gba or prequel did narratively. Part of that discussion however is any solution requires less faction jumping. It's not exactly that RD fell on its face with supports, it's the odd structure hindered how well the characters came across. They definitely lose something with too much group hopping. Onsomble stories are difficult to balance like that, and no other games do not even bother to try much at all. RD definitely tried too hard to have things come together from too many ends.
On the blood pact... I just don't see how it's any worse than most games being driven by "lol magic man make bad things happen because crazy shit like bad things happen" or "dragon racism" or "oh no plot convient events". It's just more convenient magic shit that happens in every game, especially the new ones that are typically heavily front loaded with a ton of that shit.
Like waiting til 10 games into a series that corrupting magic is suddenly a big issue is silly, or at the very least a rather rose tinted look at things. I think people exaggerate it recontextualizing things. Sure it provides excuses but it's not like it absolves those characters from all their past actions. I'm sure some people would prefer years worth of lore dumping politics that of course was everyone's favorite shit of the prequel star wars movies, and fans of the idea would call anyone that disagrees something like that would have made the story more boring as "childish and stupid". This already is that same shit that just has some degree of actual insurance that is more of an issue to deal with. I agree it's execution could have been better, but underwritten and fucking terrible are a bit different.
I take much more issue with awakening world building garbaging being the most basic bitch multiversial garbage that fucking stains the entire series with overly convenient nonsense. That actually had long term negative effects on the writing of multiple games.
And as far as stupid choices go, I have to remember that bad magic man in 1 gives Marth the only 2 tools capable of fucking everything they caused because...? And that game doesn't have a prequel that established the major players all making pretty damn utilitarian decisions. Like you have immense amounts of groundwork pointing to how often folks involved jump to brutal tribalistic action just because they see that as the most desirable thing to do. Adding more layers to solving the problem than "just stop" or "kill the bad ones" doesn't exist to say no one is to blame, but shift what the potential solutions to the problem are.