I think approaching a utopia like the TOS era is more interesting than actually being in a utopia like the TNG era. Everything in TNG revolves around the Prime Directive - Prime Directive this, Prime Directive that. Picard doesn't ever shut the fuck up about the Prime Directive. The Prime Directive was basically kryptonite that prevented every conflict from being easily solved by the OP Federation. That line of story telling was fine for that time, but I don't think we need it again. I guess they could make it so that there's a breakdown of society after Voyager, but fans would probably riot about that.
TOS had a heck of a lot Prime Directive talk too. It's pretty fundamental to every series in the franchise really, except for Enterprise.