I stopped posting early this year. The introduction of the spur.us/mcl.io fingerprinters (which they put between the Cloudflare and 4chan captchas) made me think about what I was willing to tolerate, and with most threads being shit, the choice was easy.
Now I just lurk, and knowing I won't post in any threads keeps my lurking limited. So my impressions of current 4chan may be out of date.

>Are there any boards that are still fun to use?
Only if you embrace the trolling as a way of life. Allegedly, the slowest, nichest hobby boards there are better insulated from the rot.
>If I use the filter mechanism to block out shit threads is it enjoyable?
The problem with filters is there's always a new form of shit, and mods won't do their jobs of deleting low quality posts and whacking repeat offenders with the banhammer. Now a loonie problem has festered in every recurring thread on every board, and when one of the crazies do get banned they just wait three days and do it all again, or ban evade completely.
>it feels like there is almost nothing worth reading there. Even having a conversation is basically impossible
There were faint glimmers of light during my last months there, but yeah it's very dim.