Upgrades are bad for your LD game. Here is why.
I played a few games here that have an upgrade mechanics, most of them implement kind of vampire survivors upgrade system with 3 random choice upgrades (like on the picture below)

In fact, I encountered it so many times, I started to feel weird about my game implementing this as well (if you want to try another game with upgrades, feel free to check out Doom Scrolling - roguelike about bottom of your short videos app)
Even though the upgrade system clicks in Vampire Survivors I have a controversial opinion that it might be harmful for the LD entry.
The upgrade system works in VS because it matters and it matters for two reasons:
* 1. Without it game is still fun *
If you remove upgrades from VS, and leave only one ability the game will obviously miss a lot, but it will still be fun to play for 4-5 minutes. The reason is because the core gameplay loop is fun - you have enemies around, and you need to maneuver between them so you can hit them and avoid being hit yourself. The number of enemies on screen becomes bigger in time, so it becomes more challenging to keep alive and number of seconds you survive could be a indicator of your skill which you can use for competition with other players, or the game designer can use as a game goal. Note, that people will play your LD game for 5-10 minutes tops (unless they are super hooked), so while it's not great for steam release, if your LD game is enjoyable for this timeframe you did a great job.
* 2. Without upgrade system Vampire Survivors is much more difficult and becomes unplayable quick enough *
While core gameplay loop tests your dexterity/reaction skills, upgrades/meta tests your strategic planning skills - how good can you choose upgrades to keep up with bending challenge curve? Upgrades add another dimension to the game, Without it you can compete for seconds of the gameplay, with it you compete for minutes of additional gameplay time.
What's wrong with LD games with upgrades?
Most of the games with upgrades I saw lack either 1 or 2 of the above criteria. If your core gameplay loop is not polished enough and doesn't click, upgrade system doesn't make it better. There is not much motivation to search for upgrades and explore upgrade tree if the core game is boring. At the same time, if you can complete the game without a single upgrade - the whole system also doesn't make any sense (you could've just removed it).
Why could upgrade system be harmful for your LD entry?
LD is very time constraint event and you must prioritize properly, otherwise you can't finish with something playable. Without polished core gameplay, upgrade system doesn't add to you game. This means that time spent on developing the system is taken from time you could spend on polishing core, and in the end it means you spent your time on nothing, not making your game better, but wasting your precious effort and time.
Well polished core gameplay without upgrades is always better than average bland core gameplay but with.
What do you think? Feel free to comment here if you saw a great entry this LD of game with upgrades, or let me know if you think I am wrong, I am always happy to chat :)
If you think a guy writing a post like this created a great game - you are wrong :) I think I fell in the same trap this time, but if you don't mind, feel free to try my game out - here is the link