Although I have not watched S4 yet, unfortunately, I can agree to this, since it happens to all shows.
I would modify the statement to be: "enjoy this series while you can, for it will most likely become a show with no direction (no pun intended) in the next decade(s)." I've seen countless shows go down a path and never come back up.... I'm just hoping this one doesn't die too quickly because it's going strong from what I've watched so far.
Then again, we could have "that one show" where it just is good. I mean, many of the shows out there have to do with life's dramas and issues as well as the somewhat more frequently occurring mild-humor/puns.
On the other hand, this show also has to do with life's dramas and issues.... and how to deal with them, humor and puns.... but suited for all age groups, as well as something the majority of popular shows don't have these days: core values for life (i.e. friendship, respect, etc)
Final comment.... Let's not bash the guy. It's his own opinion, and although he brought it on himself to put his opinions out in the open, it doesn't mean that we need to tear his opinions apart. It's just an opinion.