Re definitely was something that just going to be the happy ending version of Tokyo Ghoul at the start but over time it gained it's own themes alongside the original's(this part is personal preference but I like how the themes of Re are much clearer to decipher on the first read through). Suzuya had minimal character development throughout Re until the ending that's for sure but saying he seems like a robot here is the correct observation as he's making most of his decisions based on what he thinks other great leaders would do instead of what he thinks he should do(Tldr It was on purpose.). The best parts of Tokyo Ghoul are the psychological parts so yes the dramatic monologues are good, and much preferable to Tokyo Ghoul where 70% of the text on screen is common sense as to how he should fight, though the hair thing is kinda stupid it's meant to represent the changes in Kaneki's mentality which gives it a pass.Re's important characters get to develop plenty they may not have as much screentime as the OG cast but they do ultimately get a good amount of character development. Ultimately Re wasn't really the mess you made it out to be.All of :Re was a goddamn mess. I've always thought of the true end of the series being TG with :Re as fanfic for the people who couldn't stomach the original.
I can't tell if Ishida was forced into making :Re or what but just lots of missed opportunity and things that could have been done for the better. For example in TG we get introduced to the concept that Kakuho could be farmed from ghouls with high enough regenerative abilities, then that Kakuja are insanely rare and could be harvested to produce Quinque Armor-types. There is absolutely no reason why CCG wouldn't just harvest Kaneki at that point.
More stuff that got foreshadowed was the concept that people Kaneki 'ate' he had hallucinations of. Even in TG this seemed to be true, and at the end of TG:Re Kaneki sees every person he ever ate. Why not in TG:Re the Q's have hallucinations of their own counterpart. Haise could have been a giant red herring until we find out that Kaneki is hidden in Cochlea being farmed as a guinea pig. This would've reinforced why Haise would want to do the prison-break beyond saving Hinami. We also could have begun to CARE about Haise instead of him being a throwaway persona. Also the Q's needed more time to get developed. None of them got anywhere NEAR the development of the original cast, or any OC :Re character in fact. The loss of fodder characters every arc also led to this problem. People would get a chapter of development and then get killed off for shock value. I really don't care if you want them to die as an author but don't be so eager about it. Let them have their moment to shine and stew for a little while before jumping to that action.
And on that note, every arc didn't need to be the size of Anteiku raid. Too goddamn many bloated arcs with disposable characters who all die by the end of the arc. I'm looking at you Rose arc. Hell even the first main arc with the Auction scrapped a bunch of fodder that were being developed. We also don't need dramatic monologues in the middle of every fight and then Kaneki 'changing' mid-fight to overcome his opponent saying something edgy while his hair turns a new color. This happened once in TG and like four times (?) in :Re.
I think Ishida also fucked up by having Furuta at the end of TG. The more I thought about it the less sense it makes. Why would Kaneki recall some randy clown he's never met just because he's dying. Wouldn't it have made more sense for the person to have dropped the beams to have been Arima? Y'know because he was working on Kanou's orders. Also that he would remember Arima's face now because he just now met him again and would think 'I remember him from before'. Furuta got spoiled so fucking fast because of this stuff. Not like he was a decent character to begin with but still.
And don't even get me started on how much of a stale brick Suzuya was this entire time. No character development at all, he was such a fun character we saw go from a heartless monster to someone who was more human by the end of TG. He just seems like a robot here.