We probably have to accept the change in tone and pace: Womanizer Charlie has been replaced by sissie Walden. Not perfect to me, but we know the background of it.
And of course Walden has changed the entire scenery. Not another womanizer, so obviously he needs a permanent girlfriend and stuff.
But still: His girlfriend Zoey and his ex Bridget are neither funny, nor interesting. Nor sexy or at least important.
And even Lindsey starts to get quite annoying.
They (authors, producers and such) try so hard, to avoid any similarities to the "Charlie Sheen" era, that it all feels unnatural and forced.
Get relaxed! It's a sitcom. Not a drama. So draft some not-so-forced SITuations and at least try to have some COMic situations. But PLEASE, I'm begging you, don't go back to farting, puking. And I don't need Gorillas either.
Personally, I think about letting it go after that season. Maybe 9 seasons is enough anyway?