Personally I put "Bad design" down as "Things that hinder the core function or purpose of the project".
Tick-Tack-Toe or Rock-Paper-Scissors don't really have any 'bad' design points, but rather are examples of beautifully simple designs. Tick-Tack-Toe's game-draw 'issue' isn't a bad design in my view, but rather a fun quirk that makes it such a great logic and learning tool.
So we need to draw some lines and start to think about things like 'core purpose', how design elements relate to it, and whether a design actually improves or hinders things in that specific instance for a given project. And we also have to draw a divide between Mechanics design, and Interface design. You can have a great core mechanic of how things work, but the overarching design fails due to issues with how you interact with it, and you can have a great interaction design, but overall still fail because it doesn't really connect to any good core mechanics. - You can make the prettiest and most awesome button in the world to keep on your desk, but it isn't all that great of a project if it isn't hooked up to anything.
The bit of a niche market of "Frustratingly hard platformers" typically has a design mechanic that will include easy and very common ways to die. The fact that you are running along and die often due to things like falling down a bit, hitting the wrong wall tie, etc is not, in and of itself, a 'bad design' element, but rather it makes up a fundamental aspect of the project's core purpose. They're Supposed to be frustrating, as that's kind of the point of the game - Overcoming the insanely difficult puzzle and not dying. But design elements still must be judged on a case-by-case basis.
If you have a mechanic where the character may completely and totally randomly just die and you lose, regardless of any input from the user or choices they may have made, then odds are it is probably something readily filed under "Bad design". However if you break the design down that is essentially the core mechanic of slot machines and many addictive gambling related games. - You select your bets, pull the lever, and odds are you probably 'die', and you lose. But every now and then you don't lose, and that triggers all the special happy things in some people's brains.
Try to imagine a slot machine that allowed you to learn the 'exact right way' to pull the handle such that every single time you pulled it you 'won', and you could sit there pulling it exactly right each and every time for hours on end, constantly winning... Those slot machine mobile apps are weird enough for me to try to understand why anyone plays them (Since they don't actually have payouts, but you can still do in-app purchases), but I struggle to think of an audience who could be entertained by being able to constantly win something like that.
Then we can take sound core mechanics, and look at what happens when 'bad' UI design is applied to them. I think my most recent favourite example for this would be Subnautica and how its UI functions in its current state. Namely, the inconsistencies in backing out of menus/game states.
Hit tab to open or close your PDA - Simple enough...
But, if you watch live streamers try it for the first time (And I myself found this issue too), while you're on that 'menu' for the PDA/Inventory/etc screen, users naturally want to hit ESC to back out of it... But that just opens the "Game Menu/Pause Screen". This is something that you eventually can learn to get around, but it breaks a 'natural convention' in the computing world, which is why it is so common to catch new users doing it.
In and of itself, it isn't a 'bad' design, but rather it is more a 'less than ideal' design.
But things get worse...
Soon after starting the game you get a tool that allows you to open a 'building menu', which looks and feels a lot like the PDA/Inventory menu. That's obviously closed out by hitting the TAB key, as we've been 'trained' by the game with the PDA, right? ... Well, wrong. You click off to the side of the screen to close that one...
Eventually we get the Seamoth or the Prawn suit, vehicles that you can enter by clicking on them... But you exit them with the E key.
And it 'gets worse' when you get the large Cyclops and use the camera mode while piloting it - You right click to back out of it, or hit ESC... So in this case ESC doesn't open the Pause Menu, but backs you out of the camera to the main piloting station view, where upon ESC will then once again open the Pause Menu when pressed. Why? Because... Reasons?
Then there are bad design issues like the Seamoth, the first 'proper' sub you get training you to turn your lights on and off with a mouse button, and the game teaching you that some of the 'less than friendly creatures' you might encounter don't respond in all that positive nature to having new lights show up in their environment... But when you get to the Prawn Suit? Left click 'punches' with the left arm, right click with the right arm... And I have no idea how to turn the lights off in that thing. (But on the other hand, running around and punching/drilling the stuff that used to kill you and make you terrified of the sea does have a sort of giddy pleasure to it, so I eventually stopped caring about whether the lights were on and if I were hidden or not, and just adopted a "Bring it on motherf...." attitude.)
On top of that there are the 'bad designs' with inventory items, chest mechanics, and tools and the hotbar. Some objects will 'auto add' themselves to your 5 slot tool bar if you click on them, shifting all the other slots to the right. So you'll have your stasis rifle, knife, seaglide, scanner, and build tool in slots 1, 2, 3, 4,and 5, and an accidental click on the wrong thing? Well, now instead of 'deploying' the gravity net thing in the water, you've shifted things on your toolbar by one slot and put the gravity net in slot 1... So you have to go back and rekey all your tools.
Moving things between chests? Well that's a right click. But a left click will eat stuff, and it is mildly easy to accidentally eat a bunch of things early on rather than putting them in chests. Easy enough to learn around, but then you'll get the battery chargers... Which not only use left click to move things be the charger and your inventory, but unlike your inventory and storage chests the items in the chargers will STAY in their spots. If you wanted to move a bunch of batteries from a chest you would keep clicking the top-left one on the screen as the rest would move up/over to auto-compact the list.
Swapping batteries in your tools? Well, some tools will clearly show their battery level on screen when you pull them out, other's won't show it but still consume battery power and force you to manually check its level. And the list of different batteries you can swap to doesn't order itself with "Highest charged first", making it easy to accidentally pop a battery you just took from one tool into another. Plus the whole having to manually double check batteries/charge cells in your inventory when putting them in the charging station. (And lets not talk about the annoyance that is the Cyclops Engine Room when it comes to installing upgrades and swapping out power cells.)
Subnautica has a bunch of random different 'bad design' issues. It isn't a "Bad Game", the forty or so hours I've put into it since getting it a week or so ago would suggest that it very much isn't a bad game, but being a good and fun game doesn't exempt it from having bad designs included. Subnautica's "Bad Designs" are mostly down to inconsistencies, and 'false training' of the user compared to content that they will see later on as they play more. It isn't earth shattering-game breaking bad, but man it could be so much smoother and consistent to play if they had a little more User Experience design thought put into it.