All the apps make it very difficult to create a post. You have to know what community you will be posting to, search for the community, click the three dots, click create post, click whether it’s a photo/link/text and then start posting.
Why not just have a Create Post button with the title field, url field, body text field, and a button to upload a photo and then a choose community button
Majority are very Reddit app like where it’s exactly as you described and that would be why. There wasn’t a general post button. You always posted within the subreddit, at least in all the ones I used.