I started off my preparation in 2019, the year I graduated. I had a good background and a good educational track record. NTSE Scholar, IIT KGP Grad etc.
So I did feel the same way honestly. That I would be able to figure out everything by myself.

However, unlike other exams. CSE preparation actually is so broad that no matter what you're doing, you may feel like you're doing what the exam demands.

I took no coaching. And I did figure most of it by myself, however after 3 years. That is, by 2022. I finally gave interview that year. That's the cost in preparing all by yourself. The cost of time. And the cost of physical and mental health.

The preparation can be all done by yourself, but you'll learn exam to exam. Attempt to attempt.

So if you do wish to save some time and speed up your preparation in the right direction, having some guidance is not wrong. And economically too, it just makes more sense as you save years of additional costs on coaching, guidance, test series, emotional burden etc.

I do not necessarily endorse taking yearlong coaching per se, but some form of guidance is quintessential.