@SateriCat17 is right about the common assurance that these games really are
just that hard and them requiring a lot of repetition and practice to 1CC them even on normal isn't something going wrong or some weakness on your part but just a necessary process to learn the game. I've come to enjoy the process of learning to 1CC each game.
There are still some common pain points that a new player might hit.
1) I find that new players try to hold on to their bombs too much. If you are regularly dying with bombs left, them you are being too conservative with them. Any death with a bomb left is a bomb wasted. Take it as a sign to be less cautious with them. You can always pull back if you find yourself dying
too much with no bombs left.
2) Many attacks you can read and react to as they happen, but each game to varying degrees does have points where a bit of memorization of what is to come next in the stage and how to avoid it is very helpful. I find practicing individual stages really helped me build strategies that I would employ in a full run.
3) Make sure to focus using shift. Simple advice, but there've been folks who ignored that feature before.
Overall though, reassure yourself that the process is going to take a good amount of time and deaths, and enjoy every small bit of progress that you make. The amount of work required to do good in these games are what makes victory so sweet. On some of the harder challenges I've beaten I'll have my hands shaking at the end out of excitement. Other games don't do that to me.