Yeah Reddit's kind of annoying to use if your account is new. 😅 From what I understand, you gotta start by commenting on other people's posts and show you're an active member to "build karma" (credibility) before posting to some subreddits.
r/IndieDev and r/gamedevscreens are good ones to start with, since a lot of devs post WIP and ask questions there to get feedback.