I think it's unreasonable to expect everyone to read every post.

It's completely natural to prioritise the posts that interest you, so I wouldn't beat yourself up about not reading everything all at once or skimming over some posts because everyone does it. One of the nice things about playing in games like this is that you can look back, having read the posts that were initially interesting to you, and take the time to read some of the work that perhaps wasn't instantly relevant to your character or your posts and find some real gems in there.