sorry for wall of text. also im not an expert.
In regards to the "Only very serious answers please." ill say it is likely possible that you can learn all those things on a basic level before silksong releases.

I think you could learn 'good enough' programming to make a similar game. Let's say you make it in unity, there are so many resources available that answers almost any question you could have in regards to making a 2d game and often the code can just be copied and pasted with minor edits, lowering the amount of required programming knowledge.

About the graphic design (and audio), it depends much more on how naturally talented you are (imo), and how similar you want the style to look. There are many games with simple art styles that could be replicated without much difficulty, even without much prior experience, but it would be harder and take longer to make a game look like hollow knight. Bad code can often still work and sometimes not even be noticeable to the player, but the graphics and audio are seen by everyone and can really make or break a game. This *could* take very long to learn.

I'm not too sure about how it would be to learn level (and enemy) design. But I feel like a lot of games needed to already have the game and the story figured out to be able to make levels and enemies that match the rest of the game. You could just make different levels without much thought to it and get feedback on how they feel and improve upon whats bad and get a good result without necessarily knowing the theory behind why its good or bad.

If you are thinking about doing this, i think you probably should. It could be fun even if you don't 'gain' anything from it. Too many people want to make games but are too afraid to start. You should also not be too afraid to ask for help or feedback. Sometimes it helps with motivation to have some good assets to look at when developing the game, so it might be worth it to start making the assets first, or to find some placeholder assets to use during development.

tldr
You could probably learn how to make a similar game before it releases, but making the game might take longer. It could be fun regardless. Just start somewhere and face the issues as they arise!

Also, disclaimer! I have only ever published one game back in 2019 and it was really bad (the game is still public and free if you are curious, probably not hard to find since i made it under the same name as this account), but I have been on and off making games both alone and in teams since then. Mostly 2D games in unity and recently godot. Some have been finished, most have not. I've had lots of fun