Well it depends upon your goals. If your target is to simply become a hobbyist programmer then frankly whatever make you happy is all you need.

However if your goal is to get a job in the industry that is a different matter. This is even more so with the advent of AI where the industries need for idiot code monkeys is going away. So if your goal is professional employment in the computing industry, which is extremely broad job wise, I have to say the background of an equivalent CS degree is mandatory. I'm not familiar with OSSU, but if completion of that program is acceptable in industry then continue to go forwards with it.

Here is the the thing people often will say you don't need XXXX class taught in a CS program, that could be anything from Calculus, to Physics, to a DSA class. One day the boss will walk up to you and ask you to do something and you are not going to have the depth of knowledge to move forward. It might be a bit of calculus you never learned or work on optimizing a bit of code that needs a sound understanding of DSA and performance on your chosen hardware and you are again blocked due to a lack of knowledge. Yes many a programmer survives n industry by doing the minimal and never complaining about why they are never promoted, but it is often about effort and drive.

There is a third avenue that you need to consider which is somebody learning to program to enhance their capability in another domain. This might be a an Electrical Engineer, focused on board support packages, an architect trying to automate a CAD activity, or a doctor... The list goes on and on, but the point here is that learning programming is a goal that enhances their ability to leverage software in their job. These people don't need the "whole program" so to speak as they have already accomplished much already. Actually it is for people like this that bootcamps often make sense. They are effectively adding onto an already strong educational background.

So for the most part I think the people that say you don't need to study that deeply are the very people that are being laid off these days. If you are looking for. a job in the industry it pays to soak up as much knowledge as is possible when you are learning easily. Knowledge is power.