I just really don't think that I can improve and become a great CaS maker
Firstly, if you're just fishing for attention and compliments, then maybe you really should get your thread deleted. Arrogance puts people off from giving honest feedback, if any feedback at all. However, I'd like to give you the benefit of the doubt and believe that you're being genuine.
If you want to stop making CaS, that doesn't necessitate deleting pictures of the ones you've already made. They're not going to get in the way of what you want to do from here and they don't offend anyone.
More importantly, you're taking CaS too seriously. It's just part of a video game. This subforum isn't some kind of league, where you have to be the best of the best in order to stay in. Yes, people here can be very critical and we have our competitions, but we do what we do so that everyone can make better CaS, not to find out who's the best. You just need to be willing to learn and participate in conversation. You've been doing great at that thus far.
Look at the names you've mentioned. Do you think they were always as good as they were now? They may have been very skilled initially from their first posts, but all of them are much more skilled today than when they started a year or more ago. You, on the other hand, have only been here for about two and a half weeks, definitely not enough time to build a decent portfolio. You're selling your potential short.
I don't know what your personal situation is and whether or not your dissatisfaction with CaS is giving you a hard time or something else is depressing you and, in turn, making you feel bad about your work. Either way, if you feel you really need to, take a break, then come back and decide whether or not you really want to stop.