Getting feedback is an important part of improving. It's arguably the most important aspect, as without it, you can get lost in the void figuring things out without the right knowledge. Getting someone knowledgable to playtest and/or look at your charts can be invaluable, and sometimes can even help you figure out something you've been stuck on for a very long time. It's extremely important to try and get feedback, and to take that feedback positively.
There are a few places you can get feedback, the most accessible of which is the charting channels in the Official Etterna Online discord, where numerous other experienced charters will look at your stuff and give their opinions. Another way is by asking people directly through the charter feedback spreadsheet, where charters and playtesters have excplicitly requested to be added to the sheet, so everyone on it is happy to recieve charts to review. There's also a tried and true method of just submitting your charts to packs. Even if your chart gets rejected, the feedback you can recieve from that rejection can be amazing for learning what you did wrong!
Getting people to playtest your stuff is incredibly useful for seeing other peoples opinions, but unfortunately resources for getting consistent playtesting don't fully exist. There's a section on the charter feedback spreadsheet, however outside of that you have to get lucky and catch someone streaming and willing to take WIPS, or message a charter or player and hope they play it. Thanks to this, I have decided to start doing consistent feedback/playtest streams every Sunday on my Twitch channel. No matter who you are, or how good you are at charting, I will provide feedback and try playtest your stuff! You can find me on my twitch account! I don't like to self advertise, but the lack of resources for consistent playtesting are something I want to try rectify. If another resource comes to light that also provides consistent playtesting access, I will remove this section from the charting advice page!