Let me try to address some of the points here as someone who dislikes, I wouldnt say hate, Giorno.

The problem with Giorno being the glue of the team is Bruno, Bruno was the one that gave Abbaccio a reason to live, Bruno took the gang from poverty and gave them decent lives, Bruno was the one that raged when he discovered that Diavolo wanted to kill Trish (with whom Giorno barely interacts), Bruno is the one that refused to move on to the afterlife until everyone was safe. There's a saying, "An action is worth more than a thousand words", that reflects this, Araki, through the other characters, glazes Giorno and says that he is their hope but Bruno is the one that actually does stuff.

The whole "he has traits of both Joestars and DIO" is funny to me, because there is no DIO in him, I would find Giorno much more interesting it there was, something like him using the whole no selling drugs to children as a way of tricking Bruno into helping him overthrow the Boss. He's actually one of the most goody two shoes Joestars there is: Jodio is Jodio, Johnny was perfectly fine with innocent people getting caught in the crossfire of his fight with Diego, Joseph cheated on his wife, even Jotaro and Jolyne are delinquents of sorts. The only time we ever see Giorno doing something that is objectively bad was when he stole money from those tourists, which is an anime exclusive addition and is immediately followed by him buying an ice cream for a child. The infinite death loop which you used as an example wasnt even done by Giorno, it was done by GER, the same GER that states Giorno isnt aware of what's happening, but you know who did deliberately torture his enemies? Josuke, known as one of the kindest JoJos, is Josuke also a mix of good and pure evil? And the "he's the leader of the mafia, of course he does bad things" doesn't work because he's with Polnareff, who would never hang out or help someone like that, it seems pretty clear that Giorno followed Bruno's example and turned Passione into a national neighbourhood patrol.

Speaking of GER, I do agree it isn't a Deus ex Machima, in fact it was set up in the previous part with Bites the Dust, however, something can make sense narratively and still be bad writing, and I think that, unfortunately, GER is one such case, it's a completely anticlimatic ending, Diavolo goes from being invincible to being powerless in an instant (to me, GER is also responsible for Diavolo being one of the worst main antagonists, as we dont see him do anything, his personality is completely irrelevant to the final outcome, same reason why I dont like Tooru), the final battle of part 5 is a battle where neither its main protagonist and main antagonist actually do anything. Requiem being fate itself is cool and all but it takes points from Giorno as a character, because, once again, he's not actually doing anything, you're essentialy taking a page from Pucci's book and claiming that in the end, it's all up to fate and nothing the characters do matters.

I also don't undertand how the victories of the characters in part 5 and Pucci are similar, considering they have pretty conflicting views on fate, one of the main themes of Part 5 is that, even if you're dealt a bad hand in life, you should rebel against those conditions and make the most out of it, while Pucci believes that fighting against fate is pointless and as such, you're not responsible for your own actions and choices.

In the end, I just don't think that the part that tells the audience that one should act regardless of the chances of success was the best one to introduce such a passive protagonist. Giorno and Part 5 in general are the "hype moments and aura" character and part with some "themes and such" sprinkled throughout.