I can't speak as an outsider, because I've been an insider to this set of games since the original SimCity.
What I have noticed from what might be considered an outsider's perspective is that the packs get very little mainstream game media attention these days, except to point out people complaining about the new bugs that each one introduces. Up to about half way through TS3, each major new pack in The Sims series got the typical game review coverage that one sees with new games or major expansions of games. The attitude now seems to be "just more of the same, so why bother covering it".
TS1 was the original experiment to see if people would find a lightweight life simulator interesting. We did. And back at the time, there was an expectation that eventually the city simulator and the people simulator would merge into a rich unified gaming experience as technology progressed. That didn't happen, and the Sim City franchise moved into its own niche product, focused more on expanding the city simulator to incorporating wider geographic areas. The Sims franchise moved in its own direction, first trying more complex life simulation with TS2, and then flirting with a small bit of town-level simulation in TS3.
Those were as close as we ever got to genuine product innovation. TS4 abandoned even the pretense of attempting to move the series forward. Thus, it has become a niche product (and a very profitable one!), where most of the publicity comes from insiders ("game changers"), rather than the larger gaming community.
I do wonder if the mystery sims game that Paradox is working on will take a shot at the SimCity / The Sims hybrid that two decades ago we thought we'd eventually see. I guess we'll find out someday -- maybe.
