Disagreed. Helpers should help people out, and it's important that they have forum posts. If you don't wanna take your time to help people out on the forums, or if you're not active, maybe then you just shouldn't try to get helper rank yet.
I understand 20 quality posts sounds like a lot, I've been there myself. But a staff member should know his way around the forums, which is shown in the posts. On top of that, it also gives a view on how the person communicates. As staff member, communication is a very important thing. By having the 20 posts and the discord activity, the communication can be checked.
As a person who *loves* forums as a platform, I strongly disagree...
Forums give a place for people to share ideas that aren't really limited by a word count (like social media such as Twitter, and minecraft chat max length). I wish Manacube's forums could be more active outside of people trying to "farm" forum posts. The people that do make up the active forum community here are really great and have good discussions! I find it worthwhile to read and learn about the people here. It'll probably help you out in general.
Of course, with forums as with most things in life, you'll get out of it what you put into it. When you put in posts that are less than a sentence long, you probably aren't going to get much out of the experience and feel like it's "just pointless tbh". So try to put some thought into your responses to others and threads you make! It'll be more fun for you.
A small sidebar with 20 being the minimum requirement, you will see that it is suggested you try to exceed these requirements to make yourself stand out. Before you apply for staff again, I'd say you should try to put in more than 20, thoughtful, full responses or threads.