Add a "like" option!

A like is equivalent to "some random agrees with your post for no discernible reason". I mean there's no reason, no identifier, and no context, just a number the poster can mistakenly fuel their ego with. Rather than quality posting they will post for easy likes.

Do you really want this place to be the next Facebook or Tumblr?

It isn't enough to say that you agree with a post, it is better to say "why" you agree with a post. I mean you all have opinions don't you? The whole point of forums is to encourage discussion.

Also, I think it would be better if we could just like threads instead of the posts.

We did have that pre xF. As Xemous said, nobody ever used it.

As to your last point: I'm pretty sure avoiding shitposts altogether is a better outcome than deleting and punishing a huge number of shitposts. "Prevention is better than cure", yadda yadda...

The images are little more than an extension of postcounts, which acts no differently. You would need to nix postcounts entirely to make what you suggest a viable option.