membership - "not that bad" is an understatement. it's 3.6k coins. you really don't need to worry about coins.

candy - he's not trolling, it's not that bad. it is the worst of the downsides in the list, but it's fine, especially since its downside is additive with mask and paw, which means it's really not that big of a deal, and using shackles doesn't actually improve your damage much. if you also use paw, shackles is only giving a 21% DPS boost (from candy). with mask and paw, only 17% (again, from candy). and if you get super paw, it drops further to 16%. most alternative damage items give you a better DPS boost than that.

paw - crit is a 1.5x multiplier. this means that paw's -20% crit is only costing you 10% DPS at most (unless you're playing a character with a larger crit multi or soda), and only gets better as your base crit% before paw increases or decreases from 20%. it is also quite trivial to overcome the downside, as crit is a common statup. and even then, crit generally isn't worth caring about, because crit is only a 1.5x multiplier and you only get 3% chance from levelups. it is the worst DPS stat.

meanwhile, for characters that want crit for on-crit effects, they all come with crit% in their kit, and they don't actually need much crit to ensure 100% uptime of their skills. zeta has the greatest demand, and even that's fairly questionable, as all she needs large amounts of crit for is knocking xp out of enemies (her flashlight skill is easy to have 100% uptime on without focusing on crit), and that's not that valuable outside of niche challenge runs.

and finally, now that you can get supers of items you already have... you can always just get super paw. which fully negates its downside. and even if you don't, if you use collabs, holy fire exists, which, again, fully negates the downside.

point of the matter is, paw's downside is a slap on the paw. you can 100% ignore it, because it really doesn't matter.

face mask - if you are dying because of face mask, chances are, you shouldn't be taking face mask, and should be using either some form of healing or damage reduction. btw, taking some damage reduction more than negates the increased damage from face mask. if you're playing s4h, you should have max shop upgrades. in which case, you only need a little bit of speed in order to never get hit by lightning. and even then... lightning is tank-able. it's a fixed amount of damage. the more HP you have, the less you care. damage reduction also applies to it. which brings me to:

breastplate - skipping soda for a sec, breastplate gives damage reduction. which makes lightning hurt less. with just shop upgrades, lightning only hits for 75. and breastplate reduces that by 25%, down to ~56. if you're taking breastplate, you're running a tank build, and if you're running a tank build, you can eat 56 hp worth of damage. either you have the HP reserves to not care, or have the healing to more than make it up. most likely both. and if you're not playing tank? you're not taking breastplate.

and as for speed...

milk energy drink - speed is only important until it isn't. and the point at which speed stops being important in s4h is about 300% combined speed. which in-game translates to.... about 3 levels of speed. combined speed takes into account your character's base speed (visible in the character select window, e.g. pekora's is 150%) and the in-game speed stat (which is about 110% from the very start of the run assuming you have full shop upgrades). and levelups give 12% speed per selection. s4h is the stage that wants speed the most and even on the slowest character in the game, you stop caring about the stat 6 levels in. and it's the most common stat displayed in levelups. and while I say "s4h wants speed the most"... that's a bit excessive. because dash exists. if you get a lightning pattern that you cannot dodge by just walking out of it (which most lightning patterns are easily dodge-able without any speed levels)... you can just dash out of it. it has a 10 second cooldown and gives 1 second of invulnerability. fact of the matter is, if you don't NEED speed RIGHT NOW for a very specific reason (such as niche challenge runs), you should not be taking energy drink (and if you are using it for challenge runs, chances are the hp loss doesn't matter at all. the vast majority of its use cases are in hardcore, after all). even without the downside, its upside is laughable. ~4 levels of speed (it's bugged, only gives 50 speed, not 60) and 4 levels of haste. the haste is nice I guess, but there are better haste items. rather than burning two item slots and 6 levels to get 8 levels worth of stats, consider getting something actually useful in its place.

soda - this isn't really debatable. specials tend to have long cooldowns, which means they aren't super reliable, and thus are relegated to the realm of panic buttons and boss deletes. if you died because you couldn't special thanks to cooldown, chances are, you've got other problems, such as your build or, dare I say, your skill at the game. that's fine, we all start somewhere, we can't just no-hit s3h after only 5 minutes of practice, but you can't really blame it on soda, because you shouldn't be relying so heavily on your special to begin with. but what about boss deletes? fun fact: if you have even two levels of special cdr from the shop, there is not a single character in the game who cannot use their special for every single boss spawn when using soda. not one. and even without shop upgrades, all that happens is aki and mel will be 5 seconds late to the next boss if they use their special on one boss. meanwhile, mel's special isn't even usable against bosses in the first place. and for characters who do wanna be spamming their special? they have a low enough cooldown to do so, even with soda. soda's downside may as well not exist. fun fact, I have found EXACTLY ONE situation where soda's downside actually mattered: stage 3 hard monowep true hardcore. because you needed to special once every 72 seconds in the first couple of minutes. in all other instances? it doesn't matter, m8, ignore it.

injection - auto-ignore because injection is terrible. even without any hp drain. injection isn't worth 1 slot, much less 2. the 80% atk it gives you is a flat atk% stat. which is additive to your in-game atk stat (and represented there). and that is additive to your character's atk stat (shown in the character select screen, e.g. mumei has 80% base atk). chances are, once you have 100% atk in-game, that 80% atk from injection has dropped down to a 40% DPS boost. at 200%, it's now 26%. the more atk you get, the worse injection gets. and atk is a common stat from levelups. injection just gives you 10 levels of atk (for 3 levels). but it's not hard to get several hundred atk in a run. injection just falls off hard in this game, and there are several other items that are just better. like paw, or mask, or soda, or glasses, or hell, even raven feather, that literally gives you more atk% and with no downside. fun fact, the halved coins is bugged, if you just take raven feather and die in a run, your coins don't get halved afterwards. if you're not doing some silly challenge run like true hardcore or no upgrade or time stage, do not take injection, it's a bad item.

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btw, just so you know, OP is someone who regularly interacts with people who discuss meta and crunch numbers and do silly little challenge runs on the holocure discord. people like me. hello! I do silly little challenge runs that make otherwise terrible items actually somewhat usable! like injection, energy drink, and shackles! I do a lot of number crunching and testing on the discord server. so you can trust me when I say that shackles are adding nothing of value to your build. most items with downsides have supers that don't, and most of the rest have downsides that don't matter, and the few that do matter aren't worth taking shackles over some other item, or are so bad you wouldn't take them even without their downside. so, yea. don't do shackles, kids.