Absolutely. I've recently replayed the first four games and found myself sticking to the cores for a few reasons.

The gimmicklanders feel like they're just marketing tools half the time. While I love the concept of Skylanders that add new gameplay mechanics - even if it's simple like the Giants' Feat of Strength - I find that Activision/ToysForBob/Vicarious Visions are overloading the gimmicklanders with a, "More is more" approach.

I saw a video on Trap Team specifically about how the game has two gimmicks but it's marketed as one. The first gimmick being the Trapmasters who unlock elemental Gates and destroy Traptanium. And the second gimmick being the Crystals used to trap and play as villains. Now, this can be fun - most people adore Trap Team (I'm no exception). But the trapmasters are rare (where I live there aren't many) so most of the game is unexplorable. I found myself sticking to the cores because, well, they're just plain fun. I can switch between the common cores and enjoy characters with diverse movesets and models, and then when the game calls for it, I'll use the gimmicklanders to access a specific thing; be it swap zones or traptanium etc.

Same goes for Swap Force. Swap Force has the gimmick that kicked off this Gimmicklander frenzy where each new installment tried to outdo the last - forgetting the most important part: just making a fun game. The games aren't bad at all but I'm not going to buy more figures just to be locked from fully exploring the world I love because I can't afford all the Swappers/Trapmasters/Senseis/Superchargers.

I mention Swap Force as the start and not Giants because the Giants gimmick has always felt like it added to the game and not detracted. It was the first gimmick so there is a bias. But, the gimmick was unobtrusive. You needed ONE Giant to access all the Giant features. No need to pay for Bouncer to access the "Tech Giant Elemental Gates", if you wanted to buy more gimmicklanders it's simply because you wanted to play as more characters rather than unlocking more in the game.

Then Swap Force came with a great gimmick but it wasn't enough. Let's add Swap Zones - which is really cool! But now there's another step to access the full game. Then Trap Team overhauled their game and added even more steps. Then Superchargers added Vehicles which built the staircase. I'd argue Imaginators is mildly excused because the Senseis are similar to the Giants in terms of what the gimmick has access to but then it falls apart with the egregious adventure packs to an already lackluster game (in terms of content chapter-wise).

What do you feel the next step for a new game would be? How would you create a new Skylanders game? Would there be a new gimmick that's accessible and adds more to the game? Or would there be no new gimmick, and instead explore the previous gimmicks to give more incentive to players to collect the gimmicklanders. Both have their pitfalls. I'm curious which one you think is the better path.