I sometimes hear that someone doesn’t want to post an idea because they feel like they would have to write a whole post, and it would need to be long, complex, and fully fleshed out.
I think short and simple Forum posts are fine — in fact, it’s often better for a post to be significantly shorter. (You could also consider making it a Quick take.)
Shortforms may sometimes be good ideas, but it’s important that people recognize that shortforms are much less viewed than normal posts (or at least so I’ve heard and sensed, and I can speak to my own personal engagement which is far less for shortforms).
Shortforms are useful for when you don't want the large audience. You might be writing especially quickly and might be debating whether to post at all.
Something I do sometimes is write a shortform and then link it to people I know. That way I've written something publicly, but I still get the feedback I'm interested in.