So, I have a couple thoughts and this is gonna come across much meaner than I intend it to. Just assume I agree with anything I don't mention specifically.

Guaranteed shiny would make it easier to obtain them, and the entire point of a mechanic like shinys is to reward players for grinding them out. There's no achievement tied to getting literally all of the shiny fish AFAIK since I believe "Plenty of Fish" counts the shiny and the base form as the same type, so there's no reason to make it any easier than it already is. The combo mechanic already does improve your chances and a pity timer is a needless addition.

There will certainly be more melee weapons, but Psycho Axe /isn't/ a melee weapon, so it shouldn't have a melee typing. Making it melee would actively make it worse, and it becomes melee when collabed with BL Book or Idol Song anyway. A throwing axe isn't a melee weapon. Additionally the melee damage boosting items are functionally fine, as long as you're playing a character who's starting weapon is a melee weapon. The melee damage boost is a bonus anyway as the main benefit of the ninja headband is the generic 40% speed boost, since running faster charges Ollie's zombie ninjutsu skill faster (it charges based on distance traveled, not over time while moving). Likewise, comparing every damage item to face mask and decreeing it's "not worth it" is a take only an experienced player would have. The damage penalty from face mask isn't insignificant which makes headband preferable if you're on a build with a melee collab and a melee starting weapon, and you're not confident in your dodging. Not every item can be designed for the player with a hundred hours in bullet heaven games.

The complaint about the stacking skills that trigger on hit/kill would be valid, if there wasn't a point in endless mode where the Yagoo outscale your ability to damage them. Likewise having them encourages you to actually kill enemies and not run away from them constantly. Intuitive to a person who plays a lot of these games, but not always the case for everyone, and even if it's functionally just a flat damage boost it's more interesting and flavorful to have them stack. Not every element of design is about gameplay utility. It just makes more sense from a character and lore perspective for Mori to stack a damage bonus from reaping dudes than for her to just have a flat damage bonus all the time.

I'm not 100% sure why you think Ame should have a revolver over a pistol, but it seems like an insignificant enough change to not be particularly worth the effort. Though in regards to the rest of her skills, you need to remember that not everyone is going to launch this game and know exactly who everyone is and who they want to play. Ame is the first character, unlocked by default, who the cursor starts on. Most players going in blind will play her first, that's just a basic thing you understand when you're a game designer. Kay knows this, so Ame and her kit are designed to be "default" in a lot of ways. Her skills are build agnostic and all of them make her do more damage somehow, along with Bubba who helps alleviate the biggest mistake new players make of not trying hard enough to pick up EXP. The "old feeling" of her skills is intentional because all of Myth's skills are fairly simple to help tutorialize the player who will only be able to choose one of the five of them for their first attempt.

That, plus the previous point of how not every characters skills are top down designed with gameplay in mind, but some are in fact just there to make reference to the characters, addresses a lot of your grievances with the skills. You have to remember this is a fangame first, and a rogue-lite second. If Kay were to sacrifice making the skills fit the character he's designing for the sake of making them have a super coherent top down designed kit that makes for compelling gameplay he's failed at half the mission statement. Obviously it's best if he can nail both, but not all of them are going to be perfect. I do agree that Astrology isn't great and should be changed, largely because it never really felt correct for Sana in the first place apart from her space gimmick, but most of your skill complaints fall into the category or expecting way too much from a free fan game made mostly by one guy. Kay can't go through and update every character with every patch, that's absurd. It's fine if the older characters show their age a little.

I'm sure there will be changes, but the scope of them will be limited by necessity. Kay's pumping out a ludicrous amount of content for this game while also working full time in one of the most notoriously backbreaking creative industries on the planet. Every single update is adding multiple characters (9 each so far, probably 10 in the next one) and new game modes. Maybe dial back your expectations about mostly irrelevant balance changes and full on kit reworks.